6.5 Biological Hazards: Recognition & Exposure Control

6.5 Biological Hazards: Recognition & Exposure Control

Biological hazards (biohazards) are living organisms, or substances produced by living organisms, that can cause illness, infection, allergic reaction, or toxic effect in exposed workers. STS5 Domain 4 opens with "identify hazards related to biological issues," placing biological agents alongside chemical, physical, airborne, and ergonomic stressors as a core industrial hygiene category.

Biological hazards differ from the chemical hazards in Sections 5.2 and 5.3 in one decisive way: they reproduce. A chemical spill is a fixed quantity that disperses or degrades. A bacterial or fungal colonization amplifies as long as it has moisture, nutrients, and a hospitable temperature — which is why the supervisory control is so often about eliminating the growth condition rather than cleaning up the agent.

---

1. The Five Agent Classes

---

2. Where Supervisors Actually Encounter Them

• Bloodborne pathogens. Any employee whose duties create reasonably anticipated contact with blood or other potentially infectious material — designated first-aid responders, custodial staff cleaning body fluids, wastewater workers handling sharps. This is governed in detail by 29 CFR 1910.1030 and is taught with its full control chain in Section 7.3.
• Legionella. Cooling towers, evaporative condensers, decorative fountains, hot-water systems, and eyewash stations that sit stagnant between weekly flushes. Amplification occurs in the roughly 77–113 °F range; exposure occurs when the water is aerosolized. Weekly eyewash activation, required by ANSI/ISEA Z358.1, exists partly for this reason.
• Mold and water intrusion. A roof leak, a pipe failure, or a flooded bay left wet becomes a fungal amplification site. EPA guidance is that mold begins growing on damp porous materials within 24 to 48 hours, which converts drying speed into a genuine control measure.
• Histoplasmosis. Disturbing accumulated bird or bat droppings during demolition, attic work, or HVAC cleaning aerosolizes Histoplasma spores. NIOSH and the CDC treat guano-disturbing work as respirator work.
• Coccidioidomycosis (Valley Fever). Soil-disturbing work — excavation, grading, dust-generating vehicle traffic — in the arid southwestern United States. Controls are soil wetting, enclosed cabs with filtered air, and respiratory protection.
• Hantavirus. Sweeping or pressure-washing rodent-infested sheds, crawlspaces, and equipment storage aerosolizes the virus. The control is to wet down with disinfectant and avoid dry sweeping.
• Sewage and floodwater. Wastewater and flood response expose workers to enteric bacteria, hepatitis A, and Leptospira, with ingestion via contaminated hands the dominant route.
• Insect and animal contact. Tick-borne disease in grounds and utility work, and stinging-insect anaphylaxis — a bee or wasp sting in an allergic worker is a life-threatening emergency, not a nuisance.
• Organic dust and endotoxin. Grain handling, composting, and textile work produce hypersensitivity responses including farmer’s lung and byssinosis.

---

3. The Regulatory Gap: Why There Is No PEL for Mold

This is a frequent exam trap. Unlike the chemical stressors in Section 6.1, biological agents almost never carry a numerical occupational exposure limit.

[!WARNING] The sampling trap. Because there is no PEL and no recognized "safe" airborne spore count, quantitative mold air sampling rarely produces an actionable number. The defensible supervisory response to visible fungal growth is to find and stop the moisture source, dry or remove the affected material, and protect the workers doing the remediation — not to commission a spore count and wait for a threshold that does not exist.

---

4. Applying the Hierarchy of Controls to Biological Agents

1. Elimination / substitution. Repair the water intrusion; remove the guano accumulation before work begins; substitute a non-latex glove to eliminate latex protein sensitization.
2. Engineering controls. Water management and biocide treatment for cooling towers; local exhaust and containment during remediation; negative-pressure enclosures; enclosed filtered-air cabs for soil disturbance; sharps containers and self-sheathing needles, which 1910.1030 requires be evaluated and documented annually.
3. Administrative controls. Wet methods instead of dry sweeping; an exposure control plan reviewed annually; hepatitis B vaccination offered at no cost within 10 working days of initial assignment under 1910.1030(f)(2)(i); prohibiting eating, drinking, and cosmetics application in exposure areas; hand-washing facilities and a rule to wash immediately after glove removal; tick checks and light-colored clothing for outdoor crews; identifying stinging-insect-allergic workers and locating their epinephrine auto-injectors before field work.
4. PPE. Gloves appropriate to the agent, eye and face protection where splashing is anticipated, and respiratory protection — at minimum an N95 filtering facepiece for spore-generating tasks such as guano disturbance or mold remediation, with higher levels selected by a qualified person. All respirator use falls under the 1910.134 program requirements taught in Section 6.3, including medical evaluation and fit testing.

---

5. Routes of Entry and the Supervisor’s Response

Biological agents use the same four routes taught in Section 6.1:

• Inhalation — aerosolized spores, Legionella mist, hantavirus from dried droppings.
• Dermal contact or absorption — urushiol from poison ivy, Leptospira through abraded skin in floodwater.
• Ingestion — hand-to-mouth transfer after sewage or animal contact, the reason hand-washing and no-eating rules are enforceable controls rather than etiquette.
• Injection (percutaneous) — the dominant bloodborne route, via needlesticks, contaminated blades, and puncture wounds. A puncture from a dirty object also raises tetanus, which is why current tetanus immunization is a standard condition for industrial and grounds work.

When an exposure occurs, the supervisor’s duty is speed. For a bloodborne exposure incident, 1910.1030 requires a confidential medical evaluation and follow-up made immediately available, and post-exposure prophylaxis is time-critical. For a suspected biological inhalation exposure, remove the worker from the source, document the task and duration, and refer to occupational medicine — do not wait to see whether symptoms develop, because incubation periods for histoplasmosis and Valley Fever run one to three weeks after the exposure has ended.