SUBJECT: Pollution Prevention in Laboratories

What is a hazardous waste?

Knowing what chemicals are regulated as hazardous wastes provides a starting point for waste minimization. Wastes are classified as hazardous if they meet at least one of the following characteristics:

  • ignitable - they have a flash point < 140 degrees Fahrenheit or are oxidizers
  • corrosive - pH<2.0 or pH> 12.5
  • reactive - to air or water, explosive, or are a cyanide or sulfide containing compound
  • toxic - they have levels of certain metals, solvents, or pesticides greater than prescribed limits

A number of chemicals are also listed as hazardous if they become wastes. There are the P-list of acutely toxic materials and the U-list of toxic materials. Metals of concern for the toxic characteristic are arsenic, barium, cadmium, chromium, lead, mercury, selenium and silver.

How to start - Setting up a new lab

  1. Think about the potential hazard of every chemical you intend to use
  2. Keep a clean house
    • Keep an updated inventory with locations indicated
    • Label and date chemicals
    • Keep the lab orderly and clean
  3. Centralize chemical purchases through one person in lab
    • Check chemical recycling list first
    • Purchase in smallest quantity needed
    • Share with other labs
  4. Manage wastes properly
    • Establish an area for storing chemical waste
    • Segregate waste streams as much as possible
    • Label wastes properly
  5. Consider waste generation a factor when planning experiments.

How to start - Improving an existing lab

  1. Clean-up house
    • Review all chemicals in stock for: outdated, off-spec, unneeded items
    • Dispose properly
    • Organize shelves for proper chemical storage
    • Label and date all containers
    • Prepare or update chemical inventory (include location)
    • Keep lab orderly and clean
  2. Review laboratory procedures
    • Can less hazardous or non-hazardous reagents be used?
    • Are there safer alternatives to highly toxic, reactive, carcinogenic or mutagenic materials?
    • Review procedures annually to see if quantities of chemicals and/or chemical waste can be reduced
    • New protocols and procedures
    • Consider kinds and amounts of waste
    • How can they be cut?
  3. Establish centralized purchasing system
    • One person reviews order for duplication
    • Check chemical recycling list
    • Check other labs
    • Order smallest quantity needed
  4. Evaluate disposal practices
    • Is the waste hazardous?
    • Is more segregation possible?
    • Are wastes labeled properly with names and quantities?
  5. Guidelines for planning experiments
    • The following is a brief description of chemicals to avoid when planning laboratory experiments for research, analytical or instructional purposes.

Recommendations (in order of priority):

  1. Eliminate or reduce the use of reactive chemicals, where possible, for both safety and hazardous waste reasons. If wastes from laboratory work are reactive, deactivate their reactive characteristic as part of the experiment.
  2. Eliminate or reduce the use of halogenated solvents, where possible. Many halogenated solvents are carcinogens or suspected carcinogens. If such solvents must be used, investigate redistillation to minimize disposal requirements.
  3. Reduce or eliminate the use of arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver where possible- If silver must be used, recover for reclamation.
  4. Eliminate or reduce the use of oxidizers, where possible.
  5. Eliminate or reduce the use of non-halogenated flammable solvents, where possible. Try to find non-flammable, biodegradable substitutes. If such solvents must be used, investigate redistillation to minimize disposal requirements.
  6. Eliminate or reduce the use of highly toxic chemicals, where possible.
  7. Neutralize all corrosive solutions as part of the experiment. Waste acid or base may be neutralized to a pH between 6 and 9 and then disposed of down the drain, provided that the solutions do not contain toxic materials that would classify them as hazardous wastes.


Replace hazardous or toxic materials with non-hazardous or less hazardous products.

Use the following substitutions where possible:

  • Acetamide
    • Substitute: Stearic acid
    • Comments: In phase change and freezing point depression
  • Chromic acid cleaning solutions
    • Substitute: Detergents
    • Comments: Last resorts: KOH/Ethanol bath, acid bath, or NoChromix
  • Ethyl Ether
    • Substitute: Methyl t-butyl ether
    • Comments: Avoid forming explosive peroxides
  • Formaldehyde
    • Substitute: Ethanol
    • Comments: For storage of biological specimens
  • MercuryThermometers
    • Substitute: Red liquid thermometers
    • Comments: None
  • Xylene
    • Substitute: Limonene based extract
    • Comments: For histology uses


Ways to reduce quantities of hazardous or toxic chemicals

  1. Automation/Instrumentation
    • Purchase equipment that enables the use of procedures that produce less waste.
  2. Reduced scale
    • Scale down experiments producing hazardous waste wherever possible
  3. Microscaling (in teaching labs)
    • Consider use of microscale experiments. Consider demonstrations or video presentations as a substitute for some student experiments that generate chemical wastes.
  4. Conservation of raw materials
    • When solvent is used for cleaning purposes, use spent solvent for initial cleaning and fresh solvent for final cleaning.
    • Perform work in batches


Reusing material (after processing, if needed) in original process or reclamation for use in other processes

  1. Participate in the chemical recycling program (if don't have one, get it started).
    • Examine, your waste/excess chemicals for other uses in your lab, other lab areas
    • Review list of pre-owned chemicals before purchasing chemicals
    • Inform chemical recycling coordinator of recycled chemicals you can use
    • Arrange to set up a locker or shelf of excess chemicals in a lab or stockroom in your department.
  2. Evaluate other wastes for reclamation in labs.
    • Recover silver, mercury, other heavy metals.


Rendering the products of a chemical process non-hazardous or reducing the volume of the hazardous material.

  • Look into the possibility of including detoxification and/or waste neutralization steps in laboratory experiments.
  • Neutralize wastes that don't contain heavy metals.
  • Incorporate these steps into experimental procedure.