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Molecular Biology

Hazardous Materials

Safety in the molecular biology laboratory is a dual discipline. The laboratory scientist must simultaneously manage the risk of infectious agents found in clinical specimens (Biological Safety) and the risks posed by the aggressive, mutagenic, and volatile reagents used to extract and visualize nucleic acids (Chemical Safety). Adherence to federal regulations (OSHA) and institutional guidelines is mandatory to prevent exposure incidents

Biological Safety: Handling & Disposal

The handling of human specimens (blood, bone marrow, tissue, CSF) requires the application of Standard Precautions, which dictates that all samples be treated as if known to be infectious for HIV, Hepatitis B, and other bloodborne pathogens. Because molecular workflows involve vigorous agitation, vortexing, and centrifugation, the primary biological risk is the generation of infectious aerosols

  • Engineering Controls (The Biological Safety Cabinet)
    • Class II, Type A2 BSC: This is the standard containment device for the molecular lab. It uses HEPA filters to create a curtain of air that protects the User (from pathogens), the Product (from contamination), and the Environment (from exhaust)
    • Proper Use: The sash must be held at the certified height to maintain proper inflow velocity. Air grilles (front and rear) must never be blocked by notebooks or waste bags, as this disrupts the laminar flow and allows aerosols to escape. Arms should move in and out perpendicular to the front face to avoid creating turbulence
  • Work Practice Controls
    • Centrifugation: Use sealed safety cups or aerosol-tight rotors when spinning clinical specimens. These cups should only be opened inside the BSC to contain any aerosols generated by tube breakage
    • PPE: Fluid-resistant lab coats (buttoned), nitrile gloves (latex is often insufficient for chemical resistance), and face shields (if working outside the hood) are mandatory
  • Disposal Protocols
    • Solid Waste (Red Bag): Contaminated soft items (gloves, paper towels, tubes) go into red biohazard bags
    • Sharps: Needles, scalpel blades, and glass slides must go into rigid, puncture-resistant containers. Never recap needles
    • Liquid Waste: Biological liquids are typically decontaminated with 10% Sodium Hypochlorite (Bleach) for 30 minutes before disposal. Crucial Exception: See Guanidine warning below

Chemical Safety: Handling & Disposal

Molecular biology utilizes a specific class of chemicals not found in routine chemistry or hematology labs. These include DNA-binding mutagens, volatile organic solvents, and chaotropic salts. The OSHA Hazard Communication Standard requires that Safety Data Sheets (SDS) be accessible for all chemicals and that secondary containers carry GHS labels indicating the specific hazard (e.g., Corrosive, Carcinogen, Flammable)

  • Specific Molecular Hazards
    • Ethidium Bromide (EtBr): A fluorescent dye used to visualize DNA. It is a flat molecule that intercalates (wedges) between DNA base pairs, making it a potent mutagen. It requires the use of Nitrile gloves (it penetrates latex) and must be disposed of via incineration or charcoal filtration, not poured down the sink
    • Phenol/Chloroform: Used for organic extraction. Phenol causes severe, painless chemical burns (anesthetic effect) and is corrosive. Chloroform is a volatile neurotoxin. These must be used in a Chemical Fume Hood (exhausted outside), not a Biological Safety Cabinet (recirculated air)
    • Formamide: Used in hybridization buffers; a known teratogen (reproductive toxin)
    • Acrylamide: A potent neurotoxin in its liquid/powder state (monomer). Once polymerized into a gel, it is less toxic
  • The Guanidine-Bleach Incompatibility
    • The Hazard: Lysis buffers used in silica-based extraction kits often contain Guanidine Thiocyanate
    • The Reaction: If Guanidine is mixed with Bleach (Sodium Hypochlorite), it generates toxic Cyanide Gas
    • Disposal Rule: Never pour lysis buffer waste into a bleach trap. It should be collected separately as hazardous chemical waste or neutralized according to manufacturer instructions
  • Storage & Segregation
    • Chemicals must be stored according to compatibility. Acids: must be separated from Bases. Oxidizers (like nitrates) must be separated from Flammables (like ethanol). Volatile solvents require vented storage cabinets