Before using any chemical, even if it is something that you have worked with at home or in other situations, it is important to understand what the hazards may be and how to work with it safely.
In order to assess the hazards of a particular chemical, both the physical and health hazards of the chemical must be considered. Generally, more information is available about physical hazards than health hazards. An overview of basic toxicology and physical hazards follows.
Before using any chemical, the MSDS or other appropriate sources should be reviewed to determine what conditions of use may pose a hazard. Accidents with hazardous chemicals can happen quickly and may be quite severe. The key to prevention of these accidents is awareness.
PHYSICAL HAZARDS OF CHEMICALS
The physical hazards of a chemical include its flammability and reactivity. Flammability is the tendency of a chemical to burn. The flashpoint, autoignition temperature and flammable limits of the material may be found in the MSDS, and are helpful in assessing the potential for a fire hazard under specified conditions. See section 5, Explanation of Material Safety Data Sheet Information for a more detailed explanation of these terms.
Reactivity is the potential of the material to explode or react violently with air, water or other substances upon contact. The MSDS furnishes this information in the Reactivity Data section.
HEALTH HAZARDS OF CHEMICALS
The health effects of hazardous chemicals are often less clear than the physical hazards. Data on the health effects of chemical exposure, especially from chronic exposure, are often incomplete. When discussing the health effects of chemicals, two terms are often used interchangeably - toxicity and hazard. However, the actual meanings of these words are quite different. Toxicity is the ability of a chemical substance to cause harm. Hazard is the likelihood that a material will cause harm under the conditions of use. Thus, with proper handling, even highly toxic chemicals can be used safely. Conversely, less toxic chemicals can be extremely hazardous if handled improperly.
The actual health risk of a chemical depends on the toxicity and the actual exposure. No matter how toxic the material may be, there is little risk involved unless it enters the body. An assessment of the chemical's toxicity and the possible routes of entry will help determine what protective measures should be taken.
ROUTES OF ENTRY
Skin and Eye Contact
The simplest way for chemicals to enter the body is through direct contact with the skin or eyes. Skin contact with a chemical may result in a local reaction, such as a burn or rash, or absorption into the bloodstream. Absorption into the bloodstream may then allow the chemical to cause toxic effects on other parts of the body.
The absorption of a chemical through intact skin is influenced by the health of the skin and the properties of the chemical. Skin that is dry or cracked or has lacerations offers less resistance.
Wear gloves and other protective clothing to minimize skin exposure. See Section 3, Personal Protective Equipment for more information. Symptoms of skin exposure include dry, whitened skin, redness and swelling, rashes or blisters, and itching. In the event of chemical contact on skin, rinse the affected area with water for at least 15 minutes, removing clothing while rinsing, if necessary. Seek medical attention if symptoms persist.
Chemical contact with eyes can be particularly dangerous, resulting in painful injury or blindness. Wearing safety goggles or a face shield can reduce the risk of eye contact. Eyes which have been in contact with chemicals should be rinsed immediately with water continuously for at least 15 minutes. Contact lenses should be removed while rinsingdo not delay rinsing to remove the lensesseconds count. Medical attention is necessary if symptoms persist.
The lungs are the most common route of entry for gases, vapors and particles. Such materials may harm tissue in the lungs or enter into the bloodstream.
Most chemicals have an odor that is perceptible at a certain concentration, referred to as the odor threshold. Olfactory fatigue may occur when exposed to high concentrations or after prolonged exposure to some substances. This may cause the odor to seem to diminish or disappear, while the danger of over-exposure may remain.
Symptoms of over-exposure may include headaches, increased mucus production, and eye, nose and throat irritation. Narcotic effects, including confusion, dizziness, drowsiness, or collapse, may result from exposure to some substances, including many common hydrocarbon solvents. In the event of exposure, close containers, open windows or otherwise increase ventilation, and move to fresh air. If symptoms persist, seek medical attention.
Chemicals that produce vapors should be used in a well ventilated area or in a fume hood. Occasionally, ventilation may not be adequate and a fume hood may not be practical, making it necessary to use a respirator. The use of a respirator is subject to prior review by EHS according to University policy, since their use is regulated by the federal Occupational Safety and Health Administration Respiratory Protection Standard. See Section 3, Personal Protective Equipment for more information.
The gastrointestinal tract is another possible route of entry for toxic substances. Although it is unlikely that anyone would accidentally eat a chemical, exposure may occur as a result of eating or drinking contaminated food or beverages or touching the mouth with contaminated hands. The possibility of exposure by this route may be reduced by not eating, drinking, smoking, or storing food in the areas where chemicals are used or stored and by washing hands thoroughly after working with chemicals, even when gloves are worn.
In the event of accidental ingestion, immediately go to McCosh Health Center or contact the Poison Control Center, at 800-962-1253 for instructions. Do not induce vomiting unless directed to do so by a health care professional.
The final possible route of exposure to chemicals is by accidental injection. Injection may occur through mishaps with syringe needles, or through accidents with broken glassware or other sharp objects that have been contaminated with chemicals.
If accidental injection has occurred, wash the area with soap and water and seek medical attention, if necessary. Cautious use of any sharp object is always important.
HEALTH HAZARDS OF CHEMICAL EXPOSURE
The affects of a chemical exposure to a person will vary; depending on the actual amount of the chemical to which a person was exposed and how hazardous the chemical actually is.
Toxic Effects of Chemicals
The toxic effects of a chemical may be local or systemic. Local injuries involve the area of the body in contact with the chemical. For example, if you spill an acid on your arm, the effect will be on your arm. Systemic injuries involve tissues or organs other than the contact site where toxins have been transported through the bloodstream. For example, methanol that has been swallowed may cause blindness.
Certain chemicals may affect a target organ. For example, lead primarily affects the brain, kidney and red blood cells and some solvents may harm the liver and kidneys.
It is important to distinguish between acute and chronic exposure and toxicity. Acute toxicity results from a single, short exposure. Effects usually appear quickly and are usually reversible. Chronic toxicity results from repeated exposure over a long period of time. Effects are usually delayed and gradual, and may be irreversible. For example, the acute effect of drinking alcohol is becoming drunk, while the chronic effect from drinking alcohol over a long period of time is cirrhosis of the liver.
Susceptibility of Individuals
Some people may be more or less sensitive to specific chemicals, depending on several factors including eating habits, physical condition, obesity, medical conditions, drinking and smoking, and pregnancy.
Over a period of time, regular exposure to some substances can lead to the development of an allergic rash, breathing difficulty, or other reactions. This phenomenon is referred to as sensitization. Over time, these effects may occur with exposure to smaller and smaller amounts of the chemical, but will disappear soon after the exposure stops. For reasons not fully understood, not everyone exposed to a sensitizer will experience this reaction. Examples of sensitizers include epoxy resins, nickel salts, isocyanates and formaldehyde.
Particularly Hazardous Substances
Many chemicals have been evaluated for their ability to cause cancer. The latency period for most cancers range from twenty to forty years. The risk of developing cancer from exposure to a chemical increases with the length of exposure and with the exposure concentration.
It is important to understand the distinction between human carcinogens and suspected human carcinogens. The term human carcinogen is used when there is clear evidence of the ability to cause cancer in humans. Suspected human carcinogen refers to chemicals that have been shown to cause cancer in two or more animal species and are therefore suspect in humans.
Anyone who works with, or plans to work with carcinogens or suspected carcinogens must follow strict guidelines to minimize exposure. For a particular substance, the Toxicity Data section of the Material Safety Data Sheet will state whether or not the substance is considered a carcinogen by the Occupational Safety and Health Administration (OSHA), the National Toxicology Program (NTP) or the International Agency for Research on Cancer (IARC).
Reproductive toxins are chemicals which affect the reproductive system, including mutagens (those which cause chromosomal damage), teratogens and embryotoxins. Embryotoxins may be lethal to the fertilized egg, embryo or fetus, may be teratogenic (able to cause fetal malformations), may retard growth or may cause post-natal functional deficits. Other reproductive toxins may cause sterility or may affect sperm motility.
Some chemicals may cross the placenta, effecting the fetus. A developing fetus may be more sensitive to some chemicals than its pregnant mother, particularly during the first twelve weeks of pregnancy, when the mother may not know she is pregnant. Proper handling of chemicals and use of protective equipment is especially important to reduce fetal exposure to chemicals.
Known human teratogens include organic mercury compounds, lead compounds, ionizing radiation, some drugs, alcohol ingestion, and cigarette smoking. Some substances which may cause adverse reproductive effects in males include 1,2-dibromo-3-chloropropane, cadmium, mercury, boron, lead, some pesticides, and some drugs. More than 800 chemicals have been shown to be teratogenic in animal models - many of these are suspected human teratogens.
Individuals who work with teratogens and who are contemplating pregnancy or are pregnant should review the toxicity of the chemicals in their workplace and may consult with EHS to determine whether any of the materials pose additional risk during pregnancy.
Where To Find Toxicity Information
Toxicity information may be found in Material Safety Data Sheets, under the "Health Hazard Data" section, on product labels, in the Registry of Toxic Effects of Chemical Substances (RTECS), or in many other sources listed in the Health and Safety Reference Guide on the next page. Additional information is available on the EHS web site at http://www.princeton.edu/~ehs. For more information, contact Environmental Health and Safety at x8-5294.
HEALTH AND SAFETY REFERENCE LIST
*Bretherick, I., Handbook of Reactive Chemical Hazards, 4th ed., CRC Press, 1990.
British Cryogenic Council, Cryogenics Safety Manual, 3rd ed., 1991.
*Clayton, George and F. Clayton, editors, Pattys Industrial Hygiene and Toxicology, Wiley, Interscience, 1991.
*Compressed Gas Association, Inc., Handbook of Compressed Gases, 3rd ed., VanNostrand Reinhold Company, New York, 1990.
*Gosselin, et al, Clinical Toxicology of Commercial Products, 5th ed., Williams and Wilkins, 1984.
*Hawley, Gessner G., The Condensed Chemical Dictionary, 11th ed., Van Nostrand Reinhold, Company, 1987.
*Lewis, Richard J., Dangerous Properties of Industrial Materials, 8th ed., Litton Educational Publishing, Inc., 1992.
*National Institute of Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, (published annually).
*Princeton University, Princeton University Health and Safety Guide, June 1997.
*U.S. Department of Health and Human Services, Occupational Health Guidelines for Chemical Hazards, NIOSH/OSHA.
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