20.1 Biosafety, PPE, Bloodborne Pathogens, and SDS

20.1 Biosafety, PPE, Bloodborne Pathogens, and SDS

Quick Answer: OSHA Bloodborne Pathogens requires an exposure control plan, engineering controls, and free hepatitis B vaccine for at-risk employees. Wear gloves, fluid-resistant gowns, and eye protection for splash; use a fit-tested N95 or PAPR for airborne work. No mouth pipetting, no food at the bench, sealed centrifuge cups, and a certified Class II BSC for aerosols. Most diagnostic bacteriology is BSL-2; M. tuberculosis culture and many high-risk rule-out organisms are BSL-3. Read the SDS before a phenol, formalin, or bleach spill—never mix bleach with acids, ammonia, or formaldehyde.

Official outline IV.C Safety (content guideline revised 2025-09-25) sits inside Domain IV Laboratory Operations (10–15% of M). This section is the prevention program: bloodborne pathogens, PPE, safe work practices, chemical documents, and BSL-2 versus BSL-3. Needlesticks, eyewash, fire, and shipping are 20.2. Mathematics and instruments are 20.3. IV.F Laboratory Administration (operation, management, communication, education) is SM-only and is not M-tested—do not spend exam time on staffing models, budgets, or education-program design.

Bloodborne pathogens and the OSHA program

The OSHA Bloodborne Pathogens (BBP) standard (29 CFR 1910.1030) is the legal backbone for clinical laboratories. HBV, HCV, and HIV travel in blood and other potentially infectious materials (OPIM): serum, CSF, synovial and amniotic fluids, semen, unfixed tissue, and any fluid visibly contaminated with blood. Microbiology adds cultured organisms as a second infectious class.

A compliant program has named pieces the exam tests:

1. Exposure control plan — a written list of tasks with exposure risk, the engineering and work-practice controls that reduce that risk, PPE, training, and post-exposure steps. It is reviewed at least annually and after incidents.
2. Hepatitis B vaccine — offered free to employees with reasonably anticipated occupational exposure, after training and within 10 days of assignment. Declination must be signed; the employee may reverse it later. HBV vaccine is the only pathogen-specific vaccine OSHA requires in the BBP standard; HIV and HCV have no equivalent occupational vaccine.
3. Engineering controls — devices that isolate the hazard: puncture-resistant sharps containers, safety-engineered needles, splash shields, centrifuge safety cups, and biological safety cabinets. They sit above PPE in the hierarchy of controls because they do not depend on perfect human behavior.
4. Work-practice controls — how people use those devices: no recapping of needles (one-handed scoop only if recapping is truly unavoidable), no mouth pipetting, hand hygiene after glove removal, and no food, drink, cosmetics, or contact-lens handling in the technical area.
5. Training, labels, and medical records — biohazard labels on refrigerators and waste, training at hire and at least annually, and confidential exposure and medical records retained for employment plus 30 years.

Standard precautions treat every specimen as potentially infectious. They replaced older universal-precautions language and apply to blood, OPIM, and non-intact skin. Microbiology then adds transmission-based precautions when the organism's route is known:

A CSF Gram stain with Gram-negative diplococci is a droplet event for the patient-care team; the culture of N. meningitidis is still handled in a BSC because vortexing and flaming generate aerosols. Do not confuse the patient's isolation category with the laboratory's BSL.

PPE: gloves, gowns, eyes, and respirators

Gloves (nitrile is the usual latex replacement) are worn for every specimen and culture. Change them between dirty and clean tasks, and never walk out of the laboratory wearing them. Double-gloving is used for some BSL-3 and high-titer viral work; it is not a substitute for a BSC.

Gowns are fluid-resistant. A cloth coat that soaks through is not PPE. Cover the wrists, tie the back, and remove the gown before leaving the technical area. A soaked gown is a spill—change it.

Eye and face protection (goggles or a face shield) is required when splash is reasonably anticipated: uncapping tubes, pouring discard, opening a positive blood-culture bottle, and making smears from liquid media. Prescription eyeglasses are not PPE.

Respiratory protection is not a surgical mask when the hazard is airborne. A fit-tested N95 filtering facepiece or a powered air-purifying respirator (PAPR) is required for airborne-precaution patients and for procedures that can aerosolize M. tuberculosis or other airborne agents outside a certified cabinet. A surgical mask stops droplets, not droplet nuclei. Fit testing is annual and after facial-structure change; a leaking N95 is not an N95.

A usable exam donning order is gown, then mask or respirator, then eye protection, then gloves last. Removal starts with gloves (or gown-and-gloves together), then eyes, then the respirator, then hand hygiene. Hospital SOP is the authority at work; the exam tests that the respirator comes off last so you do not inhale what just left the gown.

Safe work practices and the Class II BSC

No mouth pipetting. Mechanical pipettes exist because historical mouth pipetting transmitted Salmonella, Shigella, and Brucella.

No eating, drinking, chewing gum, applying cosmetics, or storing food in refrigerators that hold specimens or reagents. A reagent refrigerator with a biohazard sticker is still not a lunch box.

Centrifuge safety cups or sealed rotors are used for infectious specimens (sputum digests, blood, stool concentrates). Load and unload the sealed cup inside the BSC. If a tube breaks, leave the centrifuge closed for at least 30 minutes so aerosols settle, then open it in a BSC with PPE and disinfect.

Aerosol-generating procedures—vortexing, grinding tissue, sonicating, flaming loops from liquid media, opening lyophilized vials, and subculturing positive mycobacterial bottles—belong in a certified Class II biological safety cabinet. Class II protects personnel, product, and environment with HEPA-filtered downflow and exhaust. Class I protects personnel and environment but not the culture. Class III is a gas-tight glove box used at BSL-4. The common clinical cabinet is Class II A2 (partial recirculation). Do not use an A2 for volatile toxic chemicals; those need a chemical fume hood or a total-exhaust (B2) cabinet. A UV lamp is an optional extra, not a substitute for wiping the work surface with an EPA-registered intermediate-level or tuberculocidal disinfectant.

Work several inches inside the sash, do not block the front or rear grilles, and disinfect at the start and end of work and after a spill. Annual certification (and recertification after relocation) is pass/fail: an uncertified cabinet is not a BSC.

SDS, GHS pictograms, and named chemical spills

Every hazardous chemical has a Safety Data Sheet (SDS) in the 16-section GHS format. Section 2 is hazards, Section 4 first aid, Section 6 accidental release, Section 8 exposure controls, Section 11 toxicology. Read it before the spill. Pictograms the micro bench actually sees:

Phenol (phenolic disinfectants and some mycobacterial extraction methods) is corrosive and systemically toxic through skin. A phenol skin splash is wiped, then irrigated copiously; polyethylene glycol 300 or 400 is the classic decontamination aid where the SDS specifies it—do not treat phenol like a simple water-wash acid burn and walk away. Formaldehyde / 10% formalin (parasitology preservatives, some histopathology send-outs) is a sensitizer and a carcinogen; spills get the formalin kit, eye protection, and ventilation, not a casual paper-towel wipe.

Sodium hypochlorite (bleach) is the usual blood-spill disinfectant on nonporous surfaces. Many SOPs use a 1:10 dilution of household bleach (about 5–8% stock → about 0.5% available chlorine), prepared fresh. Exam arithmetic may instead start from a labeled 10% stock (20.3). Do not mix bleach with acids (chlorine gas), ammonia (chloramines), or formaldehyde (bis-chloromethyl ether, a carcinogen). Phenolic disinfectant plus bleach can also throw irritant fumes. Contain, absorb, and dispose as the SDS directs; concentrated reagent spills are chemical waste, not ordinary biohazard trash. Flammable stain solvents go in a flammable cabinet. Sodium azide can form explosive heavy-metal azides in metal drain pipes—do not dump azide down the sink.

BSL-2 versus BSL-3 for mycobacteria and select agents

BSL-2 is the default for clinical microbiology: agents that cause human disease by percutaneous, mucous-membrane, or ingestion routes, with limited aerosol risk during routine work. Restricted access, biohazard signage, a sink, an autoclave or equivalent waste stream, and a Class II BSC for aerosols define the space. Stool, urine, wound, genital, and most blood-culture work-up is BSL-2.

BSL-3 is required when the agent may cause serious or lethal disease by inhalation and when the laboratory is propagating that agent. Features include directional inward airflow, sealed penetrations, restricted access, and respiratory protection when work cannot be fully contained. Culture manipulation of M. tuberculosis is BSL-3 because a grown isolate is a concentrated aerosol (Chapter 14). Unidentified AFB from a pulmonary specimen are treated as TB until identified.

Sentinel rule-out of B. anthracis, Y. pestis, F. tularensis, and brucellosis-causing Brucella is performed in a Class II BSC using BSL-3 practices even inside a BSL-2 sentinel laboratory (Chapter 13). Confirmation belongs to the LRN. Brucella left the U.S. select-agent list on December 17, 2024; biosafety did not change—it remains a highly infectious, reportable, rule-out/refer organism and a classic laboratory-acquired infection. Do not sniff plates. Do not open-bench MALDI these isolates. Do not treat a BSL-2 door sign as permission to work a mold-like buff AFB colony on the open bench.

BSL-4 (high-consequence viral hemorrhagic fever agents) is not a hospital microbiology activity; those specimens follow public-health instruction.