Biological Hazards Reference · CIH
CIH Biological Hazards Reference
A quick-recognition table for the biohazards subject area: 27 occupational biological hazards across bacteria, fungi, viruses, parasites and non-infectious hazards. Each entry lists the exposure route, the work where exposure is more likely, typical onset, the CIH study cue and the controls that matter.
How to use this page
BGC includes infectious agents, molds, allergens, toxins and bloodborne pathogens in the CIH biohazards subject areaBGC. Individual diseases are not guaranteed exam questions, so use the table to practise the chain, not to memorize names.
- Learn the chain: source → exposure route → task and exposed worker → control → how you would verify the control works.
- The study cue is in red in each table. It is the distinguishing fact an exam question is most likely to lean on.
- A study aid, not a procedure. Higher exposure potential marks tasks where exposure can occur more readily; actual risk depends on task, intensity, susceptible workers and controls. It is not a risk group or biosafety level, and incubation periods are typical ranges, not diagnostic cutoffs.
- Fungi come in two kinds (occupational infection and indoor mold), shown as two tables in one section. Allergens and toxins made by microbes (mycotoxins and endotoxin) sit in the non-infectious section. Below the disease tables are eleven sections on evaluating and controlling biological hazards: choosing a sampler, reading spore-trap results, mold remediation, building water and Legionella, cabinets and biosafety levels, recombinant DNA work, disinfection, sanitation and hygiene, airborne infection control, the bloodborne pathogens standard, and waste and shipping.
- Every source is listed on the CIH references page. For chemical toxicants and toxins, see the Industrial Toxicology Reference.
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01 Bacterial Infections
Most of the classic zoonoses and water-system hazards. Anchor each to its reservoir and route (bird dust, birthing fluids, rodent excreta, water aerosols, ticks) before you memorize controls.
Bacterial hazards
Bacterial infectionOrganism grows in the body
Breathed in
- Legionnaires’ diseaseLegionella pneumophila · building water aerosols
- TuberculosisMycobacterium tuberculosis · infectious people
- Q feverCoxiella burnetii · birthing fluids, farm dust
- PsittacosisChlamydia psittaci · dried bird droppings
- Inhalational anthraxBacillus anthracis · spores in wool and hides
Skin, cuts, mucous membranes
- LeptospirosisLeptospira interrogans · animal urine in water
- BrucellosisBrucella spp. · animal tissue, birthing fluids
- Cutaneous anthraxBacillus anthracis · hides, wool, bone
Tick or insect bite
- Lyme diseaseBorrelia burgdorferi · Ixodes ticks
- Rocky Mountain spotted feverRickettsia rickettsii · ticks
- TularemiaFrancisella tularensis · ticks, deer flies, rabbits
Bacterial allergyImmune reaction (hypersensitivity pneumonitis)
- Farmer’s lungSaccharopolyspora rectivirgula · moldy hay
- BagassosisThermoactinomyces sacchari · moldy sugarcane bagasse
- Metalworking-fluid lungNontuberculous mycobacteria · contaminated fluid mist
Bacterial toxicityEndotoxin from gram-negative bacteria
- Organic dust toxic syndromeGrain, swine and poultry dust
- Humidifier feverContaminated humidifier water
- Byssinosis (linked)Cotton dust
The allergy agents are thermophilic actinomycetes and mycobacteria: bacteria that can look like mold. Endotoxin stays active after the bacteria die, so a culture that grows nothing does not rule it out. Brucellosis and tularemia can also be breathed in, especially in laboratories.
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Psittacosis Chlamydia psittaci | Primarily inhalation of contaminated bird dust; less commonly bites or beak-to-mouth contact | Poultry farmers and processing workers; bird breeders; pet-shop, aviary, veterinary, and zoo workers; bird-cage cleaners | 5–14 days | Bird exposure, especially dried droppings and respiratory secretions; parrots, turkeys, and ducks | Wet cleaning; dust control; veterinary management of infected birds; task-appropriate respiratory protection and gloves Source: CDC |
| Anthrax Bacillus anthracis | Skin inoculation; inhalation; ingestion | Wool, hide, and animal-hair processors; tannery workers; livestock and slaughterhouse workers; veterinarians; relevant laboratory workers | Varies by form; commonly days, but inhalational disease may be delayed for weeks | Spore-forming bacterium; wool-sorter’s disease means inhalational anthrax | Control contaminated animal products and dust; appropriate PPE; vaccination for designated at-risk groups; specialist decontamination and laboratory containment Sources: CDC, EID |
| Brucellosis Brucella spp., including B. abortus, B. melitensis, B. suis, and B. canis | Ingestion; inhalation; broken-skin or mucous-membrane exposure; accidental inoculation | Slaughterhouse workers; livestock farmers; veterinarians; animal-birthing assistants; laboratory workers | Usually 2–4 weeks; can range from days to months | Raw dairy; infected reproductive tissues and fluids; undulant fever; laboratory aerosol hazard | Pasteurization; animal disease control; gloves and splash protection; safe sharps practices; laboratory aerosol containment Sources: CDC 1, CDC 2 |
| Tularemia Francisella tularensis | Tick/deer-fly bites; infected animal tissue contact; inhalation; ingestion | Wildlife handlers; animal-control workers; veterinarians; landscapers and groundskeepers; forestry workers; laboratory workers | Usually 3–5 days; range 1–14 days | Rabbit fever; animal handling, vectors, and contaminated aerosols are distinct exposure scenarios | Vector protection; gloves for animal handling; avoid contaminated dust/aerosols; appropriate laboratory containment Source: CDC |
| Q fever Coxiella burnetii | Primarily inhalation of contaminated aerosols/dust; less commonly ingestion | Sheep, goat, and cattle farmers, especially during birthing; veterinarians; slaughterhouse workers; animal-research workers; contaminated-bedding cleaners | Usually 2–3 weeks | Placenta, birth fluids, and contaminated farm dust; environmentally persistent organism | Contain and safely dispose of birthing materials; dust control; hygiene; pasteurization; task-based PPE Source: CDC |
| Leptospirosis Pathogenic Leptospira spp., including L. interrogans | Contaminated urine/water contacting broken skin or mucous membranes; ingestion | Sewer and wastewater workers; flood-cleanup crews; farmers; veterinarians; slaughterhouse workers | Usually 5–14 days; range 2–30 days | Animal urine in water or wet soil; exposure does not require an animal bite | Avoid contaminated water where feasible; waterproof gloves and boots; cover cuts; rodent control; hygiene Source: CDC |
| Legionnaires’ disease Legionella spp., commonly L. pneumophila | Inhalation of contaminated water aerosols; less commonly aspiration | Cooling-tower cleaners and maintenance workers; building water-system workers; plumbers; spa-maintenance workers; workers near contaminated aerosols | Usually 2–14 days | Building-water systems, biofilm, and stagnation; legionellosis also includes Pontiac fever, which has a different illness pattern | Water-management program; control temperature, disinfectant residuals, stagnation, sediment, and biofilm; maintain aerosol-generating equipment Sources: CDC 1, CDC 2, CDC 3 |
| Tuberculosis Mycobacterium tuberculosis | Inhalation of infectious airborne particles | Healthcare and respiratory-care workers; correctional-facility and homeless-shelter staff; mycobacteriology laboratory workers; autopsy personnel | Active disease has no single short incubation; skin-test reactivity usually develops in 2–8 weeks | Test conversion is not active-disease onset; latent infection is not infectious | Early recognition; airborne infection isolation rooms; ventilation; appropriate N95 or higher respiratory protection; screening and exposure follow-up Sources: CDC 1, CDC 2, CDC 3 |
| Lyme disease Borrelia burgdorferi and related Lyme-causing species | Infected Ixodes tick bites | Forestry workers; landscapers; groundskeepers; farmers; park staff; surveyors; outdoor utility and field crews | Early symptoms usually 3–30 days | Tick habitat and geographic distribution; erythema migrans does not always resemble a bull’s-eye | Tick avoidance; repellents; permethrin-treated clothing; tick checks and prompt removal Source: CDC |
| Rocky Mountain spotted fever Rickettsia rickettsii | Infected tick bites | Forestry workers; landscapers; farmers; park staff; surveyors; other outdoor workers in areas with infected ticks | Usually 3–12 days | Tick species vary geographically; rash may begin on wrists/ankles but can be absent early | Tick protection; prompt tick removal; prompt medical evaluation for illness; do not wait for a classic rash Sources: CDC, MMWR |
02 Fungal Infections and Mold
One fungus can appear in both worlds, so decide first which question you are being asked. Infection is almost all inhalation of spores from disturbed soil or droppings, and its controls story is dust suppression, not disinfection; building mold is a moisture and sampling story.
Fungal / mold hazards
Fungal infectionInvasive organism grows in the body
Can infect healthy workers
- HistoplasmosisHistoplasma · bird and bat droppings
- CoccidioidomycosisCoccidioides · dry desert soil
- BlastomycosisBlastomyces · moist soil, decaying wood
Mainly opportunistic or skin route
- AspergillosisAspergillus fumigatus · compost, construction dust; immunocompromised
- CryptococcosisCryptococcus · bird droppings, soil; immunocompromised
- SporotrichosisSporothrix · enters through a cut or thorn, not inhaled
Fungal allergyImmune reaction (hypersensitivity pneumonitis)
- Farmer’s lung*Moldy hay and grain
- Bagassosis*Moldy sugarcane bagasse
- Maple bark diseaseCryptostroma corticale · maple bark
Common indoor molds
- Alternaria, Cladosporium, Penicillium, AspergillusRunny nose and asthma; severe mainly in people already sensitized
Fungal toxicityChemical metabolite (mycotoxin)
- AflatoxicosisAspergillus flavus · contaminated grain and nuts; liver
- StachybotrytoxicosisStachybotrys · water-damaged cellulose
- Ochratoxin AAspergillus and Penicillium · stored crops; kidney
* Mainly caused by thermophilic actinomycetes, which are bacteria that grow like molds; fungi contribute to farmer’s lung. The exam may still list both under “fungal” hypersensitivity. Stachybotrytoxicosis is documented mainly in animals; in buildings, the human evidence is weaker. The same fungus can appear in more than one branch: Aspergillus infects, sensitizes and makes toxins.
| Category | The question | Main examples | Sampling focus |
|---|---|---|---|
| A. Occupational or environmental fungal infection | Could an environmental source expose workers to pathogenic fungi? | Histoplasma, Coccidioides, Blastomyces, Aspergillus, Cryptococcus, Sporothrix | Soil, droppings, contaminated material, and task or exposure assessment |
| B. Indoor or building mold | What mold is in the building, and what is the exposure? | Aspergillus, Penicillium, Cladosporium, Alternaria, Stachybotrys, Fusarium | Air, surface, bulk and dust |
| C. The person | Does this worker have the disease? | Any of the above | Clinical specimen and clinical testing, not environmental samples |
A. Occupational and environmental fungal infection
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Histoplasmosis Histoplasma capsulatum species complex | Inhalation of airborne fungal spores | Demolition and construction workers; poultry-house cleaners; attic-remediation crews; cave workers; farmers and landscapers disturbing contaminated soil | 3–17 days | Soil/material enriched with bird or bat droppings; disturbance releases spores | Prevent droppings accumulation; controlled wetting and dust suppression; safe removal; risk-based respiratory protection; do not rely on bleach to disinfect soil Sources: CDC, NIOSH 1, NIOSH 2 |
| Coccidioidomycosis / Valley fever Coccidioides immitis and C. posadasii | Inhalation of airborne fungal spores | Construction and excavation workers in endemic areas; agricultural workers; archaeologists; utility-trenching and road crews | Usually 1–3 weeks | Disturbed soil in endemic areas, especially the southwestern U.S.; geography and dust-generating tasks matter | Reduce soil disturbance and dust; enclosed filtered equipment cabs; task-appropriate respiratory protection Sources: EID, CDC |
| Blastomycosis Blastomyces spp., including B. dermatitidis | Primarily inhalation; rarely traumatic skin inoculation | Forestry, excavation, construction, and landscaping workers; outdoor crews disturbing contaminated soil or decaying organic material | Usually 3 weeks–3 months | Moist soil and decaying organic material; Great Lakes and Ohio/Mississippi River regions | Minimize dust generation and exposure during soil disturbance; task-specific engineering controls and respiratory protection Source: CDC |
| Aspergillosis Aspergillus spp., commonly A. fumigatus | Primarily inhalation of spores | Compost and agricultural workers; demolition and remediation crews; workers disturbing moldy materials or construction dust | Variable; no single useful range | Distinguish invasive infection from allergic disease; invasive disease risk depends strongly on immune status; hospital construction can expose susceptible patients | Moisture and dust control; construction infection-control assessment; sealed barriers; negative-pressure work containment; appropriate HEPA filtration Sources: CDC 1, CDC 2 |
| Cryptococcosis Cryptococcus neoformans and C. gattii species complexes | Inhalation | Bird-dropping cleanup crews; building-maintenance and demolition workers; landscapers and workers disturbing contaminated soil or wood material | Weeks–months; disease can appear years later | Bird-dropping-contaminated environments are associated with C. neoformans; trees/soil are also reservoirs; host susceptibility matters | Minimize contaminated dust aerosolization; controlled cleanup; task-appropriate PPE; account for susceptible individuals Source: CDC |
| Sporotrichosis Added topic Sporothrix spp., most often S. schenckii; S. brasiliensis in cat-associated disease | Traumatic skin inoculation: cuts, scrapes or thorn pricks contaminated with plant matter or soil; scratches or bites from infected cats. Inhalation is uncommon | Gardeners and nursery workers; forestry workers; hay balers and farm workers; veterinarians and animal-care staff where cat-associated disease occurs | Usually 1–12 weeks | Skin infection, not an inhalation disease; “rose gardener’s disease”; plant matter, hay and infected cats | Gloves, long sleeves and pants when handling plant matter or hay; avoid cats with sores; gloves and scratch/bite avoidance for veterinary staff; wash wounds promptly with soap and water Source: CDC |
B. Indoor and building mold
| Fungus | Typical setting | Main health issue | Typical sampling | CIH point |
|---|---|---|---|---|
| Aspergillus | Damp buildings, water-damaged materials, dust | Allergy, asthma, irritation; aspergillosis in susceptible people | Spore trap, culturable air, tape or swab, bulk, dust | Spores can be assessed by spore trap; culture when viability matters. Also an occupational-infection organism (table A). |
| Penicillium | Damp materials, HVAC, dust | Allergy, asthma, respiratory effects | Spore trap, culturable air, tape or swab, bulk, dust | Common indoors; culture and spore trap give different information. |
| Cladosporium | Indoor and outdoor air, damp surfaces | Allergy, asthma | Spore trap, culturable air, surface or bulk | Very common airborne mold, often dominant outdoors. |
| Alternaria | Damp materials; indoor and outdoor environments | Allergy, asthma | Spore trap, culturable air, surface or bulk | Often associated with outdoor air as well. |
| Stachybotrys chartarum | Chronically wet cellulose such as drywall and paper; needs persistent, very high moisture | Irritation and allergic effects; some strains produce mycotoxins | Bulk or material, tape lift or swab; air sampling may be less representative | Wet, sticky growth may not aerosolize, so a low airborne count does not clear the room. |
| Fusarium | Water-damaged materials, plants and soil, humid places | Allergy, irritation; opportunistic infection in susceptible people | Bulk, surface, or air and culture, depending on the investigation | More context-dependent than the common indoor molds. |
Environment vs person
An Air-O-Cell does not diagnose histoplasmosis. Environmental sampling investigates the source and exposure; clinical specimens and testing investigate the disease in the person.
Agent map
Damp building → Aspergillus, Penicillium, Cladosporium, Alternaria, Stachybotrys. Bird or bat → Histoplasma. Desert soil → Coccidioides. Soil or organic material → Blastomyces. Bird droppings → Cryptococcus. Rose thorn or cut → Sporothrix.
Sample map
Airborne → spore trap. Viable → culturable air. Surface → tape lift or swab. Material → bulk. Settled → dust. Soil or droppings → source sample. Person → clinical specimen.
Aspergillus is in both tables
It is an indoor mold in damp buildings and an occupational infection organism around compost, soil and agricultural material. Decide which question the scenario asks.
03 Viral Infections
Two very different stories: airborne rodent-borne hantavirus, and the bloodborne viruses where the sharps program, vaccination and post-exposure follow-up matter.
Viral hazards
Blood and body fluidsNeedlestick, splash, broken skin
- Hepatitis BHepatitis B virus (HBV) · vaccine available
- Hepatitis CHepatitis C virus (HCV) · no vaccine
- HIV infectionHuman immunodeficiency virus · post-exposure treatment is time-critical
Breathed inAerosols and droplets
- Hantavirus pulmonary syndromeSin Nombre virus · dust from deer mouse droppings
Healthcare examples
- InfluenzaInfluenza viruses · droplet precautions
- MeaslesMeasles virus · airborne precautions, AIIR
Bite or salivaAnimal bite, scratch or lick on broken skin
- RabiesRabies virus · bats, dogs, wildlife; pre- and post-exposure vaccination
Viruses have no allergy or toxin branch, so the useful split is the route. Influenza and measles are here as healthcare examples; see section 15 for the precautions.
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Hantavirus pulmonary syndrome Sin Nombre virus and other hantaviruses | Mainly inhalation of aerosolized rodent excreta; contaminated material contacting mucosa or broken skin; occasional bites | Workers cleaning rodent-infested buildings, cabins, sheds, or storage areas; pest-control workers; farmers; forestry and field workers; demolition crews | Usually 1–8 weeks | Deer mice are an important Sin Nombre virus reservoir; dry sweeping can aerosolize contamination | Rodent exclusion; wet disinfection before cleanup; avoid dry sweeping/vacuuming; gloves; task-based respiratory protection for higher-exposure work Sources: CDC 1, CDC 2 |
| Rabies Rabies virus | Infected saliva through bites, scratches, broken skin, or mucous membranes | Veterinarians and veterinary technicians; animal-control officers; wildlife and bat handlers; rabies laboratory workers | Usually 2–3 months; widely variable | Almost invariably fatal after symptoms develop; post-exposure prevention must precede clinical disease | Safe animal handling; pre-exposure vaccination when indicated; immediate wound washing; urgent assessment for vaccine and immune globulin as appropriate Sources: WHO, CDC |
| Hepatitis B Added topic Hepatitis B virus, HBV | Needlesticks or other percutaneous exposure; infected blood contacting mucosa or nonintact skin | Healthcare and dental workers; laboratory personnel; emergency responders; sharps-waste handlers | Weeks–months | Major bloodborne-pathogen topic; a vaccine is available | Exposure-control plan; safer sharps; appropriate PPE; hepatitis B vaccination; prompt post-exposure evaluation Source: OSHA |
| Hepatitis C Added topic Hepatitis C virus, HCV | Primarily blood exposure, especially percutaneous exposure | Healthcare and laboratory workers; emergency responders; workers handling contaminated sharps | Weeks–months; often asymptomatic | Bloodborne transmission; no vaccine; infection may remain unrecognized | Sharps prevention; standard precautions; prompt exposure reporting, testing, and medical follow-up Source: CDC |
| HIV infection Added topic Human immunodeficiency virus, HIV | Percutaneous or mucosal exposure to infectious blood/body fluids | Healthcare and laboratory workers; emergency responders; workers handling contaminated sharps | Acute illness, if present, generally develops within weeks; later disease may take years | Occupational blood exposure; ordinary workplace contact is not a transmission route; PEP is time-sensitive | Safer sharps; appropriate PPE; immediate exposure reporting; urgent medical assessment for PEP Source: CDC |
04 Prion Diseases
Not a bacterium, virus, fungus, or parasite — a misfolded, infectious protein. The exam hook is decontamination: routine autoclaving is not sufficient.
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Creutzfeldt-Jakob disease (CJD) Added topic Prion (misfolded PrP protein) | Percutaneous inoculation or mucous-membrane contact with contaminated neural tissue, cerebrospinal fluid, or improperly reprocessed instruments; routine patient contact is not a transmission route | Neurosurgeons and operating-room staff; pathologists and autopsy personnel; laboratory workers handling CNS tissue; sterile-processing and instrument-reprocessing staff | Extremely long and variable, often years to decades; once symptoms begin, classic CJD typically progresses to death within 4–5 months | Not a bacterium, virus, fungus, or parasite; routine autoclaving at 121°C does not reliably inactivate prions — enhanced protocols are required | Disposable neurosurgical instruments where feasible for suspected/confirmed cases; enhanced chemical-plus-autoclave decontamination (1N NaOH or sodium hypochlorite immersion combined with extended autoclave cycles) for reusable instruments; segregate and label suspect instruments; standard and contact precautions Sources: CDC 1, CDC 2 |
05 Parasitic Infections
Fecal-oral and waterborne. Both organisms survive chlorine to some degree, so water treatment choices are the exam hook.
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Giardiasis Giardia duodenalis; also called G. lamblia or G. intestinalis | Fecal–oral ingestion through contaminated water, food, or hands | Childcare workers; sewage/wastewater workers with fecal–oral exposure; field workers drinking untreated water; some animal-care workers | Usually 1–2 weeks | Clear-looking wilderness water may be contaminated; cysts tolerate chlorine better than many bacteria | Safe water; sanitation; handwashing; boiling or suitable cyst-removal filtration, such as absolute pore size ≤1 μm; these filters do not necessarily remove viruses Sources: CDC 1, CDC 2 |
| Cryptosporidiosis Added topic Cryptosporidium spp. | Fecal–oral ingestion; contaminated water; infected animal contact | Calf handlers; dairy-farm workers; veterinarians; childcare workers; wastewater workers | Generally within days to about two weeks | Oocysts are highly chlorine tolerant; useful comparison with Giardia | Safe water; suitable filtration or boiling; sanitation; soap-and-water handwashing; prevent fecal contamination Sources: CDC 1, CDC 2 |
06 Non-Infectious and Immune-Mediated Hazards
Biological hazards that do not require infection. Do not force these into an infection-control frame.
| Disease / agent | Main exposure routes | Tasks with higher exposure potential | Typical onset | CIH study cue | Key controls |
|---|---|---|---|---|---|
| Hypersensitivity pneumonitis / farmer’s lung Added topic Inhaled microbial or other organic antigens | Inhalation | Farmers handling moldy hay/grain; bird breeders; poultry and compost workers; workers exposed to contaminated metalworking-fluid aerosols | Variable; acute episodes can follow exposure within hours in sensitized people | Immune-mediated disease rather than infection; farmer’s lung is one example | Identify and eliminate antigen sources; moisture control; enclosure and ventilation; exposure reduction; appropriate respiratory protection Sources: NIOSH 1, NIOSH 2 |
| Organic dust toxic syndrome Added topic Mixed organic dust and microbial components | Inhalation of high concentrations of organic dust | Grain handlers; grain-bin cleaners; livestock-confinement workers; agricultural and compost workers performing heavily dusty tasks | Usually within hours after heavy exposure | Noninfectious flu-like illness; distinguish from hypersensitivity pneumonitis | Reduce dust generation; enclosure; ventilation; improved cleaning/work practices; respiratory protection Source: NIOSH |
| Damp-building mold / occupational allergens Added topic Fungal material, animal proteins, and other biological allergens | Primarily inhalation; some skin contact | Water-damage restoration and mold-remediation workers; maintenance and demolition crews; occupants of damp workplaces; laboratory-animal workers | Variable; sensitization may develop over time | Asthma, allergy, and irritation can occur without infection | Moisture/source control; remove damaged materials; enclosure and ventilation; controlled remediation; appropriate PPE Sources: NIOSH 1, NIOSH 2 |
Occupational allergens
An allergen harms only people who have become sensitized. Sensitization builds over months of exposure, and once it has happened even a trace amount can set off symptomsNIOSH. That is why the control is to stop exposure early, not to wait for complaints.
| Allergen | Who is exposed | Health effect | Controls and exam points |
|---|---|---|---|
| Laboratory animals: proteins in rat and mouse urine, saliva and dander | Animal-care technicians, researchers, cage washers | Nasal symptoms first, then asthma; 20–30% of workers develop allergy and 5–10% asthma, usually within the first 6–36 months | Ventilated cage racks and changing stations, low-dust bedding, work practices that keep bedding from becoming airborne, respiratory protection as needed Source: NIH |
| Natural rubber latex proteins | Healthcare, laboratory and food-service workers who wear latex gloves | Skin reactions and immediate allergy up to anaphylaxis; the proteins ride on glove powder into the air | Non-latex gloves, or powder-free, low-protein latex. “Hypoallergenic” does not mean latex-free. The bloodborne pathogens standard requires alternatives for allergic employees Source: OSHA |
| Enzymes: subtilisins (proteases made by Bacillus bacteria) | Detergent manufacture, food and other industries handling enzyme powders | Rhinitis and occupational asthma | Enclose the process and control dust. One of the few biological agents with a numeric limit: NIOSH REL 0.00006 mg/m³ (60-minute), no OSHA PEL Source: NIOSH |
| Dust mites, cockroaches, flour, grain and green-coffee dust | Bakers, millers, grain and food handlers, building occupants | Asthma and allergy triggers | Dust control and housekeeping, ventilation, substitution where possible Source: CDC |
Dose sets sensitization, not the reaction
Higher exposure makes sensitization more likely. After it, a very small dose can trigger a reaction, so an exposure limit protects the unsensitized far better than the sensitized worker.
Allergen vs infection vs toxin
Allergen: harms the sensitized only. Infection: the organism multiplies in the body. Toxin: a chemical effect that depends on dose, in anyone.
Toxins made by microbes
Here the harm comes from a chemical the microbe makes, not from infection. Two families come up: mycotoxins from molds and endotoxin from bacteria. Not every mold makes mycotoxins, and you cannot tell by looking; “black mold” and “toxic mold” are not species namesEPA.
| Mycotoxin | Made by | Main health effect | Where workers meet it |
|---|---|---|---|
| Aflatoxins (B1, B2, G1, G2) | Aspergillus flavus, A. parasiticus | Liver damage; liver cancer, with evidence in humans | Stored grain, peanuts and corn; grain handling and farm work Source: WHO |
| Ochratoxin A | Aspergillus and Penicillium species | Kidney damage (clearest in animals; the human cancer link is uncertain) | Grain storage and silos, coffee and dried-fruit processing Source: WHO |
| Trichothecenes: satratoxins | Stachybotrys chartarum | Irritation of skin and airways; strongly inhibit protein synthesis | Water-damaged buildings: chronically wet drywall and paper Source: NTP |
| Trichothecenes: T-2 toxin, DON | Fusarium species | Rapid irritation of skin and gut lining | Moldy grain and feed, especially oats and wheat Source: WHO |
| Ergot alkaloids | Claviceps purpurea | Blood-vessel narrowing (gangrene) and neurological effects; historic “St. Anthony’s fire” | Infected rye and wheat; mainly a food and feed poisoning Source: Review |
Mycotoxins vs endotoxin
| Feature | Mycotoxins | Endotoxin |
|---|---|---|
| What it is | Chemicals a growing mold makes as by-products, found in spores and hyphae | Lipopolysaccharide (LPS), part of the outer cell wall of gram-negative bacteriaNIOSH |
| How it gets out | Carried on spores, hyphal fragments and contaminated dust | Shed as bacteria grow and released when they break apart; stays active after the bacteria are deadNIOSH |
| Main effect | Organ toxicity (liver, kidney) and cancer, mainly when eaten in contaminated food; evidence for harm from breathing it indoors is weaker | Fever, chest tightness, cough and a drop in lung function after breathing it; linked to organic dust toxic syndrome, byssinosis and humidifier fever |
| Typical workplaces | Grain handling and storage, water-damaged buildings | Swine and poultry houses, composting, cotton processing, wastewater, grain |
| How it is measured | Chemical analysis of bulk, dust or air samples for specific toxins | Filter air sample tested with the Limulus amebocyte lysate (LAL) assay, reported in endotoxin units (EU/m³); no OSHA, ACGIH or NIOSH limitNIOSH |
Myco = mold, Endo = inside the bacterium
Mycotoxins come from molds and hit organs, mostly through food. Endotoxin comes from the gram-negative bacterial wall and causes fever and airway inflammation, mostly by breathing it in.
Dead bacteria still count
Endotoxin works whether the bacteria are alive or not. A culture that grows nothing does not rule out an endotoxin exposure: sample it on a filter and test it.
Humidifier fever vs humidifier lung
Humidifier fever is a short, flu-like illness linked to contaminated humidifier water and endotoxin. Humidifier lung is hypersensitivity pneumonitis from the same kind of source. OSHA’s technical manual groups humidifier fever with the hypersensitivity diseasesOSHA.
Organ → toxin
Liver → aflatoxin. Kidney → ochratoxin A. Skin and protein synthesis → trichothecenes. Blood vessels → ergot.
No hazard matches. Clear the search box.
07 Choosing a Sampler for the Hazard
Ask which of three things you need: the particle size, whether the organism is viable, or a specific toxin.
Biological air sampling is not routine. OSHA’s technical manual says bioaerosol sampling should follow medical or clinical reports of workplace illness, and points to ACGIH guidance for sampling, analysis and remedial actionOSHA.
| Target | Device | How it collects | Typical use |
|---|---|---|---|
| Viable fungi and bacteria, size-fractionated | Cascade impactor with agar plates (Andersen type; the classic viable model has six stages) | Air passes through stages of decreasing hole size and impacts on nutrient agar; plates are incubated afterwards, and the stage shows particle size | Hospital studies, cleanrooms and building IAQ work where size distribution matters |
| Viable fungi and bacteria, quick total screen | Single-stage agar impactor (N-6 type, BioStage) | Air impacts on one agar plate through about 400 precision holes | Rapid field screening for total culturable mold or bacteria when no size data is needed |
| Total fungal spores, live and dead | Spore-trap cassette (Air-O-Cell, Allergenco-D type) | Non-viable slit impactor; particles stick to an adhesive-coated glass slide | Routine mold inspections; the slide is read under a microscope, with no culturing |
| Airborne viruses | Liquid impinger (AGI-30, BioSampler) | Air is bubbled through a sterile buffer, so particles are collected wet and are not dried out | Respiratory-transmission studies in wards and laboratories |
| Endotoxin and glucans (bacterial and fungal toxins) | Filter cassette on a personal pump (37 mm, closed face) | Captures total airborne mass on a filter that is then analyzed in the laboratory; use the filter type and endotoxin-free handling the lab specifies | Swine and poultry houses, composting, waste processing |
Pick by the question
Size → cascade impactor. Viability → agar impactor. Total spores → spore trap. Virus → liquid impinger. Toxin → filter cassette.
Culture is not the same count as a spore trap
Culture counts only what grows on the medium and conditions used. A spore trap counts live and dead spores by appearance. The numbers answer different questions and are not interchangeable.
Memory aid: spore trap versus culture
The trap takes a photo (everything, live and dead, fast, but blurry: genus or group). The culture conducts an interview (only the living, slow, but it can name the species).
Toxins are measured, not grown
Endotoxin and glucan are quantified from mass collected on a filter, not from colonies on agar.
Culture samples: the details that get tested
| Point | What to know |
|---|---|
| Units | Colony-forming units per cubic metre of air: CFU/m³ = corrected colony count ÷ air volume sampled (m³). Example: 28.3 L/min for 2 minutes = 56.6 L = 0.0566 m³; 40 colonies ÷ 0.0566 = about 710 CFU/m³. |
| Positive-hole correction | In a multi-hole impactor, two or more particles can pass through the same hole and grow as one colony. Counts are corrected with a positive-hole table, and the correction grows as the plate fillsNIOSH. |
| Growth medium | Fungi: malt extract agar with chloramphenicol or rose bengal to hold back bacteria; DG18 for dry-loving (xerophilic) fungi. Bacteria: a general medium such as tryptic soy agar. Thermophilic actinomycetes are incubated at 50–58 °CNIOSH. |
| Sampling time | Agar dries out, so impactor samples stay short, about 20 minutes at most even where levels are low; shorten further where levels are high so plates do not overloadNIOSH. |
| Impingers | Collecting into liquid avoids the drying and impact damage that kill fragile organisms. Left too long in the liquid, some organisms keep growing and the result reads too highNIOSH. |
| Exposure limits | There are no occupational exposure limits for culturable fungal bioaerosols. Judge results against outdoor air and the building’s own history; actinomycetes indoors point to contaminationNIOSH. |
Check yourself
1A single-stage impactor runs at 28.3 L/min for 5 minutes and the plate grows 85 colonies after positive-hole correction. What is the concentration?
28.3 × 5 = 141.5 L = 0.1415 m³. 85 ÷ 0.1415 = about 600 CFU/m³.
2Why is a culture plate a poor way to measure endotoxin in a swine barn?
Endotoxin stays active in dead bacteria that will never grow on agar. Collect it on a filter and analyse it with the LAL assay.
3An investigator wants to know whether dry-loving fungi such as Aspergillus and Penicillium species are amplifying on dusty surfaces. Which agar suits that question?
DG18 (dichloran glycerol), which favours xerophilic fungi.
These are original practice scenarios. They are not BGC questions and do not predict exam content.
08 Reading Indoor Spore-Trap Results
Indoor numbers mean little alone. They are judged against an outdoor baseline taken at the same time.
| Comparison | Normal (no indoor growth source) | Points to an indoor source |
|---|---|---|
| Concentration | Total spores, and each spore type (genus or group), indoors at or below the outdoor level | A spore type significantly higher indoors than outdoors suggests an active reservoir or amplification source |
| Spore-type composition (rank order) | The types indoors, and their rank order, mirror what is found outdoors | A clearly different rank order (for example Aspergillus and Penicillium dominant indoors while Cladosporium dominates outdoors) suggests growth independent of outdoor air |
Spore types, not species
A spore trap identifies spores by how they look, so results are reported by genus or group. Aspergillus and Penicillium look alike and are reported together; a species name needs culture or DNA methodsINSPQ.
Baseline first
Take an outdoor sample at the same time as the indoor ones. Without it, an indoor count has nothing to be compared with.
A source, not a diagnosis
These comparisons describe a likely source and exposure. They say nothing about any individual’s illness.
Check yourself
1Indoor air shows Aspergillus and Penicillium dominating, while outdoors Cladosporium dominates. Total spore counts indoors and outdoors are similar. What does the comparison suggest?
A different rank order points to an indoor growth source even though the totals look alike. Compare composition as well as concentration.
2A worker develops suspected histoplasmosis after clearing an attic that held bat droppings. Would a spore-trap sample from the attic help diagnose the illness?
No. Environmental sampling investigates the source and the exposure. Diagnosis of the disease in the person needs clinical specimens and testing.
3A bulk sample of wet drywall grows Stachybotrys, but an air spore-trap sample in the room shows few spores. Is that a contradiction?
No. Stachybotrys grows in wet material and its spores may not aerosolize readily, so a low airborne count does not clear the room. The bulk or surface sample documents the source.
These are original practice scenarios. They are not BGC questions and do not predict exam content.
09 Mold Remediation
Mold is a water problem first. Fix the water, then remove the mold: killing it is not enough, because dead mold is still allergenic and some is still toxicEPA.
| Moldy area | Containment | Respiratory protection (at least) |
|---|---|---|
| Small: under about 10 ft² | None required; work carefully and keep dust down | N-95, gloves and eye protection |
| Medium: 10–100 ft² | Limited: one layer of 6-mil fire-retardant polyethylene with a slit entry and covering flap, under negative pressure | Half- or full-face air-purifying respirator with HEPA cartridges |
| Large: over 100 ft², or when occupied space could be contaminated | Full: two layers of polyethylene and a decontamination chamber or airlock, under negative pressure exhausted outdoors | Full-face powered air-purifying respirator (PAPR) with HEPA filters |
| Step | What to do |
|---|---|
| Stop the water | Find and fix the moisture source. Dry wet materials within 24–48 hours and in most cases mold will not grow. Keep indoor humidity below 60%, ideally 30–50%EPA. |
| Clean or discard | Wet vacuum only while materials are still wet. Damp-wipe hard, non-porous surfaces with water and detergent. HEPA-vacuum once everything is dry. Double-bag porous materials that cannot be saved (ceiling tile, drywall, carpet) in 6-mil polyethylene before they leave containment. |
| Biocides | Not routine. Bleach is used only when professional judgment calls for it, for example with immune-compromised occupants. Do not paint or caulk over mold. |
| Check containment | Polyethylene that billows inward shows negative pressure is holding. Sheeting that flutters outward means containment has been lost: stop and fix it. |
| Decide it is finished | The water problem is fixed; no visible mold, mold-damaged material or moldy odor remains; if samples were taken, indoor kinds and levels resemble outdoor air; and a revisit shortly after shows no new water damage or growthEPA. |
10 and 100
Under 10 ft²: no containment. 10–100 ft²: limited, one layer. Over 100 ft²: full, two layers plus an airlock. The sizes are practical guides, not health-based limits.
Remove, do not just kill
Dead spores still cause allergy. A biocide without physical removal leaves the problem in place.
Clearance = compare with outdoors
Post-remediation air samples are read like the spore-trap comparison above: indoor kinds and levels should resemble outdoor air.
10 Building Water Systems and Legionella
Legionella grows in building water, then spreads when that water becomes an aerosol. A water management program is the main control. It watches four things: sediment and biofilm, temperature, water age, and disinfectant residualCDC.
| Control point | Target | Why |
|---|---|---|
| Growth range | Best at 77–113 °F (25–45 °C); can grow from 68 °F (20 °C) | Water that sits in this band is where Legionella amplifies |
| Hot water storage | Above 140 °F (60 °C) | Keeps the heater out of the growth range; use mixing valves near fixtures to prevent scalding |
| Hot water circulating | Not below 120 °F (49 °C) | Return loops cool down and become growth sites |
| Cold water | Below 77 °F (25 °C) | Keep cold water below the growth range |
| Water age | Flush little-used outlets; remove dead legs | Stagnant water loses its disinfectant residual |
| Cooling towers | At least 25 ft from air intakes; high-efficiency drift eliminators; automated disinfectant feed; offline cleaning and disinfection at least once a yearCDC | The drift plume is the aerosol that reaches people |
Three temperatures
Store hot above 140 °F. Circulate hot at 120 °F or more. Keep cold below 77 °F. In between is the growth band.
Program, not shock
Ongoing management, based on ASHRAE Standard 188 and Guideline 12, beats one-off thermal shock, which often fails and lets Legionella recolonize quickly.
Source needs a route
Growth alone does not cause disease. There must also be an aerosol, such as cooling tower drift, a shower, a hot tub or a decorative fountain, and a susceptible person breathing it.
11 Containment: Cabinets and Biosafety Levels
Once a hazard is recognized and measured, containment is the control: the cabinet sits at the source, and the biosafety level wraps the whole room and building around itCDC.
- 1Assess the workAgent + Activity + Facility + Controls + PeopleWhat are we doing, with what, where, and who is doing it?
- 2Rank the agentRisk group = ranks the agent, not the workHow dangerous is the organism itself?
- 3Choose the box on the benchCabinet class (I to III) = the box on the benchHow much physical isolation does the task need?
- 4Choose where the exhaust goesCabinet type (Class II: A1, A2, B1, B2) = where the exhaust air goesCan anything volatile go inside, and where does the air end up?
- 5Set the roomBiosafety level (BSL-1 to BSL-4) = the roomWhat must the whole laboratory be built and run like?
Then reassess when the work, the agent or the facility changes. This is a teaching order: in practice the cabinet and the biosafety level are chosen together and revisited.
Laboratory risk assessment: what goes into it
The key idea: laboratory risk depends on both the biological agent and how people work with itCDC. A biosafety level is chosen after weighing five things.
| Factor | What you assess | Why it matters |
|---|---|---|
| Agent’s hazards | Disease severity, transmission routes, and availability of treatment or vaccination. | Different organisms pose different consequences. |
| Laboratory procedures | Centrifuging, mixing, handling sharps, and the volume or concentration used. | Some tasks generate infectious aerosols or increase exposure opportunities. Procedures that can release aerosols or droplets weigh heavily when deciding how much containment equipment and facility safeguards are neededCDC. |
| Facility design | Access control, separation and ventilation. | Helps prevent exposure outside the work area. |
| Available safeguards | Biosafety cabinets, sealed centrifuge cups, decontamination and PPE. | Controls must suit the task and the transmission route. |
| Worker health and competence | Relevant susceptibility, training, and ability to follow procedures. | Workers may differ in vulnerability and ability to work safely. |
Example: handling a closed tube is different from centrifuging a concentrated culture of the same organism. The agent is unchanged, but the procedure changes the exposure risk.
Memory aid
Agent + Activity + Facility + Controls + People
Risk groups are not biosafety levels
A risk group ranks the agent. A biosafety level is the containment chosen for the work, after a risk assessment of the agent and the procedure. A Risk Group 3 agent does not automatically mean every task needs BSL-3CDC.
| Risk group | Disease in healthy adults | Prevention or treatment | Risk | Example agents | Typical starting containment |
|---|---|---|---|---|---|
| RG1 | Not associated with disease | Not needed | No or low individual and community risk | Bacillus subtilis, non-pathogenic E. coli strains | BSL-1 |
| RG2 | Rarely serious | Often available | Moderate individual, low community risk | Salmonella, seasonal influenza viruses, hepatitis B virus | BSL-2 |
| RG3 | Serious or lethal | May be available | High individual, low community risk. Does not ordinarily spread easily from person to person | Mycobacterium tuberculosis, Yersinia pestis, SARS-CoV-1 | BSL-3 |
| RG4 | Serious or lethal | Not usually available | High individual and community risk. Spreads easily, directly or indirectly | Ebola virus, Marburg virus, smallpox virus | BSL-4 |
The last column is a starting point, not a rule. The level used for a task comes from the risk assessment of the agent and the procedure, so it can be higher or lower. Seasonal influenza is RG2, but some strains (for example H5N1) are RG3.
Biosafety cabinets: count what each class protects
| Class | Worker | Room | The work | How it works | Reach for it when |
|---|---|---|---|---|---|
| Class I | Yes | Yes | No | Open front. Room air is pulled in across the work, and the exhaust passes through a HEPA filter. | Aerosol-producing work where the sample does not have to stay sterile |
| Class II | Yes | Yes | Yes | Open front with an intake grille at the edge of the work surface. Filtered air flows down over the work, and the exhaust is filtered too; part of the air is recirculated inside. | Most infectious work at BSL-2 and BSL-3, especially when the sample must also be protected |
| Class III | Yes (full barrier) | Yes | Yes | Sealed, gas-tight glove box. Work is done through gloves fixed to the front, items pass in and out through a pass-through chamber, and both supply and exhaust air are filtered. | The highest-risk agents, as in BSL-4 work |
Three protections, then count
Worker, room, work. Class I gives two (not the work). Class II gives all three through an open front. Class III gives all three behind a sealed barrier.
Read the numbers as a ladder
I = inflow protects the person. II = adds a clean downflow that protects the sample. III = isolation, no open front at all.
Type A or Type B (Class II)
Pick by what else is in the cabinet. A types keep most of the air circulating inside. B types typically duct most or all of it outdoors, which suits work that also involves volatile toxic chemicals.
Class II cabinet types: where the exhaust goes
This table answers: can I use volatile chemicals inside? The exhaust path decidesCDC.
| Type | Recirculated | Exhausted | Where the exhaust air goes | Volatile chemicals? |
|---|---|---|---|---|
| Type A1 | 70% | 30% | Back into the lab room, or outside through a canopy (thimble) connection | Not suitable for volatile toxic chemicals |
| Type A2 | 70% | 30% | Back into the lab room, or outside through a canopy (thimble) connection; higher air intake speed than A1 | Minute amounts only, and only if exhausted outdoors |
| Type B1 | 30% | 70% | Hard-ducted outside through a dedicated duct | Minute quantities can be used routinely |
| Type B2 | 0% | 100% | Hard-ducted outside; total exhaust, nothing recirculated | Yes, as an adjunct to microbiological work; common where chemical effluent is present |
The percentages are the cabinet's design air split. Volatile chemicals are allowed only as a small adjunct to biological work: a biosafety cabinet is not a chemical fume hood, and the cabinet maker and your biosafety professional set the limits for a given cabinet.
Biosafety levels: read the number as a question
| Level | The agent | Main way you are exposed | Example agents | The rule in one line |
|---|---|---|---|---|
| BSL-1 | Does not make healthy adults ill; minimal hazard | Little concern with routine handling | E. coli K12, Lactobacillus, yeasts | Good microbiological practice and a sink |
| BSL-2 | Causes treatable disease; moderate hazard to workers, low to the community | Needle-stick or cut, swallowing, splash to eyes or mouth | Streptococcus pyogenes, Cryptosporidium, hepatitis B virus, human cell lines | Limit access, control sharps, wear PPE, use a cabinet when aerosols form |
| BSL-3 | Serious or lethal disease that can spread by aerosol; a vaccine or treatment may exist | Breathing in aerosols; also accidental self-inoculation and swallowing | Yersinia pestis, Coxiella burnetii, virulent avian influenza virus | Every infectious manipulation in a cabinet, in a room that pulls air inward and never recirculates it |
| BSL-4 | Life-threatening aerosol-borne agent with no vaccine or treatment; very high hazard, high community risk | Breathing in aerosols | Ebola virus, Lassa virus | Separate the whole facility; workers in a suit or a Class III cabinet, and a shower on the way out |
What gets added at each step
| Level | Access | Cabinet | Air | Clothing | Decontamination | People |
|---|---|---|---|---|---|---|
| BSL-1 | Doors; no special separation from general traffic | Not required | Nothing special | Basic lab clothing as the task requires | Easily cleaned surfaces and benchtops | Trained and supervised |
| BSL-2 | Limited access, traffic separated, biohazard sign | Class I or II for aerosol-producing steps | Directional flow, not recirculated | Lab coat, gloves, splash protection | Waste decontaminated before disposal; autoclave | Trained on the specific pathogen; sharps precautions |
| BSL-3 | Separate entrance, double self-closing doors | All infectious work in a cabinet with ducted exhaust | Negative pressure, all exhaust ducted outdoors, no recirculation | Solid-front protective clothing; specialized respiratory protection | Protective clothing decontaminated or discarded after use | Medical surveillance, including immunizations; a biosafety manual |
| BSL-4 | Isolated building or wing, airlock, entry and exit log | Ducted cabinet or Class III cabinet | Dedicated supply and exhaust air, plus vacuum lines | Full-body positive-pressure suit with its own air supply; change clothes before entering | All material decontaminated on the way out; exit shower | As BSL-3, plus logged entry and exit |
The stack rule
Each level keeps everything from the levels below and adds more. Learn the changes, not four separate lists.
The number as a question
1 makes healthy adults ill? no. 2 treatable? yes. 3 serious or lethal by breathing? yes. 4 serious or lethal by breathing with no vaccine or treatment? yes.
Three things step up together
Cabinet use: none, some steps, all steps, sealed. Air control: none, directional, negative and ducted, dedicated. Clothing: lab coat, solid-front, full suit.
Classic swap
BSL-2 needs a cabinet only when aerosols may form. BSL-3 needs one for all infectious work.
Lab level is not field risk
A biosafety level describes containment in a laboratory. A worker’s exposure in the field depends on the task and the controls in place.
Check yourself
1A procedure will spin a treatable bacterium in a way that can create aerosols. What is the minimum biosafety level, and what does the aerosol-producing step call for?
BSL-2, with the aerosol-producing step done in a Class I or Class II cabinet.
2Which cabinet class has an open front but still protects the worker, the room and the sample?
Class II: a HEPA-filtered downflow keeps the work sterile while air flowing in at the front protects the worker.
3A lab handles an aerosol-borne agent that causes serious disease, and a vaccine exists. Which level, and which two facility features stand out?
BSL-3. Look for negative-pressure directional airflow with all exhaust ducted outdoors and never recirculated, and double self-closing doors.
4What separates BSL-4 from BSL-3 in equipment and layout?
BSL-4 adds a full-body positive-pressure suit or a Class III cabinet, an isolated building or wing with an airlock, dedicated air and vacuum systems, and an exit shower.
These are original practice scenarios. They are not BGC questions and do not predict exam content.
12 Recombinant and Synthetic DNA Work
Genetic engineering adds one question to the usual risk assessment: what does the new construct do? In the US, the NIH Guidelines answer it through local review by an Institutional Biosafety Committee. They bind every such project at an institution that receives NIH funding for this work, whatever funds the individual projectNIH.
| Category | Review before work starts | Examples |
|---|---|---|
| III-A | NIH Director approval and IBC approval | Deliberately transferring a drug-resistance trait to a microbe that does not acquire it naturally, if that could compromise disease control |
| III-B | NIH Office of Science Policy and IBC approval | Cloning genes for toxin molecules with an LD50 below 100 ng per kg of body weight |
| III-C | IBC approval (plus other oversight) | Human gene transfer: putting recombinant DNA into research participants |
| III-D | IBC approval | Recombinant work in Risk Group 2–4 agents; whole animals; large-scale cultures over 10 L |
| III-E | IBC notice at the time work starts | Low-risk work not covered elsewhere, such as constructs with no more than two-thirds of a eukaryotic virus genome |
| III-F | Exempt (other biosafety rules, such as the BMBL, may still apply) | Certain synthetic nucleic acids and low-risk host-vector systems |
| Who | Role |
|---|---|
| Institutional Biosafety Committee (IBC) | At least five members with the expertise to judge the risk, including at least two not affiliated with the institution to represent the surrounding community. Reviews the work and sets the containment |
| Biological safety officer (BSO) | Required when the institution does BL3, BL4 or large-scale work (over 10 L); sits on the IBC |
| Principal investigator (PI) | Registers the work, follows the approved containment, trains staff and reports problems |
Start from the host
Containment begins with the risk group of the host or source organism (recombinant work in a Risk Group 2 agent is usually BL2), then is raised or lowered for what the inserted genes do.
A is for the top
III-A needs the NIH Director. III-D needs the IBC before work starts. III-E only needs notice when work starts. III-F is exempt.
BL, not BSL
The NIH Guidelines write containment as BL1–BL4, with large-scale versions (BL1-LS to BL3-LS) for cultures over 10 L. The levels match the BMBL’s BSL1–4.
13 Disinfection and Decontamination
After containment, the last control is making contaminated things safe: kill the organism, or remove it. Choose by what the item is made of and how hard the organism is to killCDC.
Hardest to easiest to kill
Bacterial spores, then mycobacteria and non-enveloped viruses, then fungi and ordinary bacteria, and easiest of all enveloped viruses. Prions are the exception: routine autoclaving is not enough (see section 04).
Kill levels
Sterilization kills everything, spores included. Disinfection is graded high, intermediate, low: the lower the level, the more organisms it leaves alive.
1. Heat, radiation and filtration
| Method | How it works | Best for | Watch out |
|---|---|---|---|
| Autoclave (moist heat) | Pressurized steam, about 121 °C at roughly 15 psi (134 °C with higher pressure and a shorter cycle) | Solid biohazard waste, glassware, instruments, culture media | Most reliable; kills spores. Steam must reach the load, and heat or moisture can damage some items |
| Dry heat | Hot-air oven, about 160–170 °C for 2–4 hours | Glassware, metal instruments, powders, oils | Slow; for items that moisture would damage |
| Incineration | Burning above about 800 °C | Pathological waste, tissues, sharps, regulated medical waste | Destroys the material rather than reusing it |
| UV-C light | 254 nm lamps damage the organism’s DNA or RNA | Surfaces and air in cabinets and rooms; water treatment | Line of sight only: shadows and dust block it |
| Ionizing radiation | Gamma rays (cobalt-60) or electron beam | Packaged single-use medical devices, tissue grafts, pharmaceuticals | Industrial process; penetrates through the packaging |
| Filtration | Traps and removes rather than kills. HEPA holds 99.97% of particles down to 0.3 µm; membrane filters of 0.22 µm clear liquids | Cabinets, isolation rooms, cleanroom air; heat-sensitive liquids such as culture media and serum | Removal, not disinfection |
2. Liquid chemicals
| Class | Examples | Use it for | Watch out |
|---|---|---|---|
| Halogens | Sodium hypochlorite: household bleach diluted about 1:10 | Spills of blood and body fluids, bench surfaces, liquid waste; the standard for bloodborne pathogens | Corrodes metals |
| Alcohols | 70% ethanol or isopropanol | Clean non-porous surfaces and electronics; kills ordinary bacteria, enveloped viruses and fungi | Does not kill spores; 70% beats 100% because water is needed |
| Aldehydes | Glutaraldehyde, orthophthalaldehyde (OPA) | High-level disinfection of heat-sensitive devices such as endoscopes | Kills spores only with a long contact time |
| Peroxygens | Hydrogen peroxide (about 3–7.5%), peracetic acid | Broad-spectrum, including spores; surface decontamination and non-invasive equipment | Concentration and contact time decide the result |
| Quaternary ammonium | Benzalkonium chloride and similar | Routine housekeeping: floors and non-critical furniture | Low level: not for non-enveloped viruses, TB or spores |
3. Gas and vapor for enclosed spaces
| Agent | Use it for | Watch out |
|---|---|---|
| Vaporized hydrogen peroxide (VHP) | Whole rooms and facilities, biosafety cabinets, cleanrooms | Leaves no toxic residue: it breaks down into water and oxygen |
| Ethylene oxide | Heat-sensitive single-use plastics, catheters, syringes, electronics | Very effective but toxic and flammable |
| Chlorine dioxide gas | Large-scale decontamination, for example anthrax-spore remediation or complex ventilation systems | Needs generation equipment and a sealed space |
Match the tool to the item
Heat-tolerant → autoclave or dry heat. Heat-sensitive → chemical or gas. Whole room or cabinet → VHP. Air → HEPA, which removes and does not kill.
Bleach or alcohol
Bleach for blood spills and bloodborne pathogens. Alcohol for clean non-porous surfaces and electronics.
Spores are the test
If a scenario names spores, think autoclave, peroxygens, aldehydes with long contact, or gas. Alcohols and quaternary ammonium fail.
Check yourself
1A blood spill on a laboratory bench needs a standard disinfectant for bloodborne pathogens. Which class, and what is its main drawback?
A halogen: diluted household bleach (about 1:10). It corrodes metals.
2Why is 70% alcohol preferred to 100% alcohol, and what will neither of them do?
Some water is needed for alcohol to denature proteins effectively, so 70% works better than 100%. Neither kills bacterial spores.
3A heat-sensitive, single-use plastic device must be sterilized. Which options fit?
Ethylene oxide gas, or radiation (gamma or electron beam) for packaged single-use devices. Ethylene oxide is toxic and flammable.
4Why is a HEPA filter not counted as disinfection?
It removes particles (99.97% at 0.3 micrometres) from the air but does not kill them.
These are original practice scenarios. They are not BGC questions and do not predict exam content.
14 Sanitation and Personal Hygiene
The oldest biohazard controls: keep the agent off hands, food and clothing, and out of the building. OSHA’s general sanitation standard sets the baseline for every workplaceOSHA.
| Element | OSHA requirement | Why it matters for biohazards |
|---|---|---|
| Potable water | Drinking-quality water for drinking, washing, cooking and cleaning; non-potable outlets clearly marked as unsafe | Stops cross-connection with process or firefighting water |
| Washing facilities | Lavatories with hot and cold (or tepid) running water, soap, and individual towels or air dryers | Handwashing is the single most important personal-hygiene control |
| Toilets and sewage | Enough toilet facilities; sewage disposal that does not endanger employees | Breaks the fecal-oral route |
| Change rooms | Where a standard requires protective clothing because of contamination: change rooms with separate storage for street clothes and protective clothing | Keeps contamination from going home |
| Showers | Where another standard requires them: one shower per 10 employees of each sex required to shower | Removal of contamination before leaving |
| Eating and drinking | No food or drink consumed or stored in toilet rooms or in any area exposed to a toxic material | No eating, drinking or storing food where contamination is possible |
| Vermin control | Workplaces built and kept to keep out rodents and insects; an ongoing extermination program where they are found | Rodents and insects carry hantavirus, leptospirosis and more |
Hands are the route
Wash hands after removing gloves, before eating, drinking or smoking, and before leaving the work area. The bloodborne pathogens standard makes handwashing after glove removal a requirement and bans eating and drinking where exposure is likelyOSHA.
Clean side, dirty side
Street clothes never touch work clothes. Contaminated clothing is laundered by the employer or disposed of, not taken home.
15 Airborne Infection Control in Healthcare
Match the precaution to how the agent travels. Standard precautions apply to every patient, and one of three transmission-based precautions is added when neededCDC.
| Precaution | How the agent spreads | What is added | Examples |
|---|---|---|---|
| Standard | Any patient: treat blood, body fluids, secretions, non-intact skin and mucous membranes as possibly infectious | Hand hygiene; gloves, gown, mask or eye protection for the expected exposure; safe injection practice; respiratory hygiene | Every patient |
| Contact | Touching the patient or contaminated surfaces | Gown and gloves | MRSA, C. difficile |
| Droplet | Large droplets over a short distance to the eyes, nose or mouth; traditionally over 5 µm and within about 3 ft, though droplets can reach 6 ft or more | Mask (facial protection) | Influenza, pertussis, meningococcal disease |
| Airborne | Small particles that stay infectious in air over long distances; droplet nuclei traditionally 5 µm or smaller | Airborne infection isolation room (AIIR) and an N95 or better respirator | Tuberculosis, measles, chickenpox |
Droplet sizes and distances are working definitions, not sharp cut-offsCDC.
| Room | Pressure | Air changes | Air handling |
|---|---|---|---|
| Airborne infection isolation (AIIR): keeps the patient’s germs in | Negative, at least 2.5 Pa (0.01 in. water gauge) | 12 per hour or more for new or renovated rooms; at least 6 for existing ones | Exhaust outdoors; if recirculation cannot be avoided, HEPA-filter the exhaust |
| Protective environment (PE): keeps germs away from an immunocompromised patient | Positive, above +2.5 Pa | More than 12 per hour | HEPA-filtered supply air |
Negative keeps it in, positive keeps it out
An infectious patient goes in a negative room. A vulnerable patient goes in a positive room. Check airflow with a manometer, smoke tube or flutter strip, with the door closed.
UV is an add-on
Upper-room or duct UV germicidal irradiation helps against airborne bacteria and viruses but cannot replace HEPA filtration, and it does little to fungal sporesCDC.
16 The Bloodborne Pathogens Standard
OSHA 29 CFR 1910.1030 covers every employee who could reasonably be expected to contact blood or other potentially infectious materials (OPIM) at work. The numbers and the order of controls are what an exam testsOSHA.
| Element | Requirement |
|---|---|
| Exposure determination | List the jobs and tasks with exposure, without regard to PPE |
| Exposure control plan | Written; available to employees; reviewed and updated at least annually and whenever tasks or positions change |
| Universal precautions | Treat all blood and OPIM as infectious; where body fluids cannot be told apart, treat all of them as infectious |
| Order of controls | Engineering and work-practice controls first (sharps with engineered injury protection, needleless systems); PPE for what remains, provided at no cost |
| Hepatitis B vaccine | Offered at no cost, after training and within 10 working days of initial assignment; employees who decline sign the declination statement and may still take the vaccine later |
| After an exposure incident | Confidential post-exposure medical evaluation and follow-up |
| Sharps containers | Closable, puncture-resistant, leakproof on the sides and bottom, labelled |
| Labels | Biohazard legend, fluorescent orange or orange-red with contrasting lettering |
| Training | At initial assignment and at least annually after that |
| Records | Medical records: duration of employment plus 30 years. Training records: 3 years. A sharps injury log for percutaneous injuries. |
The numbers
10 working days for the vaccine offer. 1 year for the plan review and for retraining. 3 years for training records. Employment +30 years for medical records.
PPE never decides who is exposed
A worker who always wears gloves is still in the exposure determination. PPE comes last in the order of controls, not first in deciding coverage.
Check yourself
1A dental hygienist always wears gloves and a face shield. Must the job appear in the exposure determination?
Yes. The determination is made without regard to PPE.
2A new phlebotomist starts on Monday. By when must the hepatitis B vaccine be offered, and what comes first?
Within 10 working days of initial assignment, after the required training. It is offered at no cost.
3How long must bloodborne pathogens training records and medical records be kept?
Training records 3 years; medical records for the duration of employment plus 30 years.
These are original practice scenarios. They are not BGC questions and do not predict exam content.
17 Biohazard Waste and Shipping
Two different rule books: OSHA says what counts as regulated waste in the workplace, and the US DOT says how infectious material is classed and packed for transport (Division 6.2)DOT.
| Category | What it means | UN number and name | Packaging |
|---|---|---|---|
| Category A | In a form that can cause permanent disability or life-threatening or fatal disease in otherwise healthy people or animals when exposure occurs | UN2814 (affecting humans) or UN2900 (affecting animals only) | Strictest infectious-substance packaging and paperwork |
| Category B | Infectious, but not in a form generally able to cause that level of disease; includes most diagnostic specimens | UN3373, “Biological substance, Category B” | Triple packaging: leakproof primary receptacle, secondary packaging, rigid outer packagingDOT |
| Regulated medical waste | Medical waste that does not contain a Category A substance | UN3291 | Waste containing Category A is shipped as Category A instead |
OSHA regulated waste
Liquid or semi-liquid blood or OPIM; items that would release it if compressed; items caked with dried blood that could flake off; contaminated sharps; pathological and microbiological waste containing blood or OPIMOSHA.
A is for awful, B is for basic
Category A = can cause severe disease on exposure (UN2814 humans, UN2900 animals). Category B = everything else infectious (UN3373), in three layers of packaging.
! Corrections and Exam Traps
Common oversimplifications, several of which make good distractors.
Risk ratings
This table does not label diseases moderate, high or critical. Occupational exposure potential, severity, biological risk group and laboratory biosafety level are different concepts.
Histoplasmosis
NIOSH reports no EPA-registered products specifically for disinfecting soil against Histoplasma. Do not use bleach spraying as a general soil-control recommendation. NIOSH
Anthrax
Brucellosis
Legionella
Use a water-management program. CDC’s potable-water guidance does not recommend thermal shock because failure and rapid recolonization are common. CDC
Tuberculosis
Routine annual TB testing is not generally recommended for U.S. healthcare personnel without known exposure or ongoing transmission; local requirements can differ. Respirator fit testing is a separate issue. CDC
Aspergillus
Negative pressure contains dust within construction work areas. Designated protective environments for susceptible patients use positive pressure and HEPA-filtered supply air. Do not confuse these pressure relationships. CDC
Rabies
Wound washing is one component of PEP. Vaccine and, for previously unvaccinated people, immune globulin may be required. Previous vaccination does not remove the need for post-exposure assessment. CDC
Giardia and Cryptosporidium
Occupational examples
The occupations column combines source-described settings with exposure-route-based examples. It is not an epidemiological ranking of disease incidence by occupation.
Prions
CIH study emphasis
Learn source → exposure route → task/exposed worker → control selection → verification of control effectiveness. The recommended additions are a study judgment, not an official exam-frequency ranking. BGC
Viable vs total counts
A culture plate reports only what grew; a spore trap reports live and dead spores. Do not treat the two numbers as the same measurement.
Stachybotrys and air sampling
Do not say it “cannot be air sampled”. Say airborne spores may be less representative because it grows in wet material and may not aerosolize readily, so bulk or surface samples can document the source better.
Environmental vs clinical sampling
Environmental samples investigate the source and exposure. Clinical specimens investigate the disease in the person. One never replaces the other.
Exam scope from BGC's certification scheme; disease and control facts from CDC, NIOSH, OSHA and WHO pages listed on the references page (links checked September 21, 2026). SPEP is not affiliated with BGC. Older publications support enduring concepts and should not override newer clinical or regulatory guidance.
