Hazardous Chemicals


"Hazardous Substance" means a substance for which there is statistically significant evidence (based on at least one study conducted according to established scientific principles), that acute or chronic health effects may occur in overexposed persons, or it is flammable, combustible, explosive, corrosive, or reactive. 

In most cases, the label will indicate if the chemical is hazardous.  Look for key words like "caution", "hazardous", "toxic", "danger", "corrosive", "irritant", or "carcinogen".  Old containers of hazardous chemicals (pre-1985) may not contain hazard warnings. 

If you are not sure whether a chemical you are using is hazardous, review the Material Safety Data Sheet (MSDS) or contact your supervisor, instructor, or the Office of Health & Safety.  

It is usually a good assumption that any chemical or chemical product is hazardous, under the OSHA definition. Remember – while most chemicals are not so dangerous that they cannot be used safely with the proper precautions, the reverse is also true; that very few, if any chemicals are so benign that they can’t cause harm in the right dose or under certain conditions! 

Types of Hazards 

Irritants are materials that can cause inflammation of the body surface with which they come in contact.  The inflammation results from concentrations far below those needed to cause corrosion.  Common irritants include substances such as: 

  • ammonia*
  • alkaline dusts and mists*
  • epoxy resins*
  • ozone
  • nitrogen dioxide*
  • phosphorus chloride

Some irritants can also cause changes in the mechanics of respiration and lung function.  These include: 

  • sulfur dioxide*
  • formaldehyde*
  • formic acid*
  • sulfuric acid*
  • acrolein*
  • halogens (e.g., chlorine)* 

Long-term exposure to respiratory irritants can result in increased mucous secretions and chronic bronchitis. 

*       These materials also have other hazardous properties. 

A primary irritant exerts no systemic toxic action, either because the products formed on the tissue of the respiratory tract are non-toxic or because the irritant action is more severe than any systemic toxic action.

A secondary irritant's effect on mucous membranes is overshadowed by a systemic effect resulting from absorption.  Examples include: 

  • hydrogen sulfide
  • aromatic hydrocarbons (e.g., benzene) 

Overexposure to a secondary irritant can result in pulmonary edema, hemorrhage and tissue necrosis. 

Simple asphyxiants, such as nitrogen, carbon dioxide, or helium, reduce the availability of oxygen by simple displacement of oxygen. 

Chemical asphyxiants render the body incapable of maintaining an adequate oxygen supply due to action at the cellular level.  They are active at very low concentrations.  Examples include: 

  • carbon monoxide
  • cyanides 

Primary anesthetics have a depressant effect upon the central nervous system, particularly the brain.  Examples include: 

  • halogenated hydrocarbons (e.g., chloroform)
  • alcohols

Chronic overexposure to hepatotoxic agents can cause damage to the liver.  Examples include: 

  • carbon tetrachloride
  • tetrachloroethane
  • methylene chloride (dichloromethane)
  • xylene 

Nephrotoxic agents can damage the kidneys.  Examples include: 

  • uranium compounds 

Neurotoxic agents can damage the nervous system.  The nervous system is especially sensitive to organometallic compounds and certain sulfide compounds.  These include: 

  • trialkyl tin compounds
  • tetraethyl lead
  • methyl mercury
  • carbon disulfide
  • organic phosphorus insecticides
  • manganese 

Some toxic agents act on the blood (hematopoietic system).  The blood cells can be directly affected or the bone marrow can be damaged.  These include: 

  • nitrites
  • aniline
  • toluidine
  • nitrobenzene
  • benzene 

There are toxic agents that can produce damage to the pulmonary tissue (lungs) but not by immediate irritant action.  Fibrotic changes can be caused by chronic overexposure to free silica and asbestos.  Other dusts can cause a restrictive disease called pneumoconiosis. 

A carcinogen” commonly refers to any agent that can initiate or speed the development of malignant or potentially malignant tumors, malignant neoplastic proliferation of cells, or cells that possess such material.  A listing of carcinogenic materials can be found in Appendix C.  Carcinogens commonly used in significant quantities include formaldehyde, benzene, ethylene oxide, and chloroform. 

“Select carcinogen” means any substance that meets one of the following criteria: 

  • It is regulated by OSHA as a carcinogen 
  • It is listed under the category, "known to be carcinogens" in the National Toxicology Program (NTP), "Annual Report of Carcinogens" (latest edition) 
  • It is listed under Group 1, "carcinogenic to humans" by the International Agency for Research on Cancer (IARC) 
  • It is listed under Group 2A or 2B by IARC or under the category "reasonably anticipated to be carcinogens" by NTP, and causes statistically significant tumor incidence in experimental animals according to any of the following criteria: 
    1. After inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime, to doses of less than 10 mg/m3 
    2. After repeated skin application of 300 mg/kg of body weight per week 
    3. After oral doses of less than 50 mg/kg of body weight per day 

“Reproductive hazard” applies to chemicals that can affect the reproductive capabilities, including chromosomal damage (mutagens) and effects on the fetus (teratogens).  A list of chemicals which can pose reproductive hazards can be found in Appendix D of this document. 

A mutagen affects the chromosome chains of exposed cells.  The effect is hereditary and becomes part of the genetic pool passed on to future generations. 

A teratogen (embryotoxic or fetotoxic agent) is an agent that interferes with normal embryonic development without damage to the mother or lethal effect on the fetus.  Effects are not hereditary. 

A sensitizer causes a majority of the exposed population to develop an allergic reaction in normal tissue after repeated exposures to the chemical.

The reaction may be as mild as a skin rash (contact dermatitis) or as severe as anaphylactic shock. 

Acutely toxic chemicals are substances falling into the following categories: 

  • A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight, when administered to albino rats weighing 200g to 300g each. 
  • A chemical that has a median lethal dose (LD50) of 2000 milligrams or less per kilogram of body weight, when administered by continuous contact for 24 hours, (or less if death occurs within 24 hours), to the bare skin of albino rabbits weighing 200g to 300g each. 
  • A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume, or less, of gas, or vapor, or 2 milligrams per liter or less, of mist, fume, or dust, when administered by continuous inhalation for one hour, (or less if death occurs within one hour), to albino rats weighing 200g to 300g each. 

A list of acutely toxic chemicals can be found in Appendix B of this document.


Gary Lee
Director of Environmental Health
4601 College Blvd.
Farmington, NM  87401
(505) 566-3063 or (505) 566-3190