
Chemicals, the Environment, and You
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fiber glass: Fine-spun filaments of glass. Fiber glass often is made into yarn that is woven into textiles, used in woolly masses as insulation, or pressed and molded as plastic material.

formaldehyde: A colorless, pungent gas used in solution as a strong disinfectant and preservative, and in the manufacture of synthetic resins and dyes.


germinate: To sprout from a seed.

hazard: A source of risk. A hazard produces risk only if organisms are exposed to it and if exposure creates the possibility of harm.


heart rate: The number of pulses of the heart in one minute.

herbicide: Chemicals developed to kill plants or regulate plant growth.

individual susceptibility: Differences in reactions between people after exposure to the same amount of a hazardous substance. A person's body size, age, gender, genetics, and health status can affect individual susceptibility.

ingestion: Swallowing (such as eating or drinking). One route of exposure to chemicals. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

inhalation: Breathing. One route of exposure to chemicals. During inhalation, chemicals can be deposited in the lungs, taken into the blood, or both.

insecticide: A chemical specifically used to kill or prevent the growth of insects.

irritant: A substance than can cause irritation of the skin, eyes, or respiratory system.

kilogram: A basic unit of mass; abbreviated kg.

LD50: The dosage of chemicals needed to produce death in 50 percent of treated organisms. LD50s are usually expressed as the weight of the chemical per unit of body weight (mg/kg). Chemicals may be fed (oral LD50), applied to the skin (dermal LD50), or administered in the form of vapors (inhalation LD50).

lead: A heavy metal that is hazardous to human health if it is breathed or swallowed.

meniscus: Curved surface of a liquid in a graduated cylinder.

mercury: A heavy metal that can accumulate in tissue of organisms in the environment and is highly toxic if breathed or swallowed.

metabolism: All the chemical reactions that enable the body to function. For example, food is metabolized (chemically changed) to supply the body with energy. Chemicals can be metabolized by the body and made either more or less harmful.

methylisocyanate: A toxic chemical used in pesticide production.

methylmercury: A human-made molecule, synthesized for commercial purposes (to kill mold), and a naturally occurring compound made by certain bacteria. Methylmercury penetrates the brain and is a potent neurotoxin. Methylmercury also crosses the placenta, and, as a result, a large number of women who were exposed during pregnancy in past methylmercury epidemics gave birth to severely brain-damaged children.

mg/kg: Milligrams per kilogram.

microgram (µg): One millionth of a gram.

milligram (mg): One thousandth of a gram.

Minamata disease: A neurological disease first identified in Minamata, Japan, as a result of mercury poisoning.

molecule: The smallest part of a compound that has all the properties of the compound; made up of two or more atoms chemically bonded.

mutagen: An agent that causes a permanent genetic change in a cell other than what occurs during normal genetic recombination. Mutagenicity is the capacity of a chemical or physical agent to cause such permanent alteration.

natural: Produced or existing in nature; not artificial or manufactured.

nervous system: Includes the brain and all the nerves.

neurotoxin: Any substance that is capable of destroying or adversely affecting nerve tissue.

National Institute of Environmental Health Sciences (NIEHS): One of the National Institutes of Health (NIH) research institutes. The mission of NIEHS is to reduce the burden of human illness and dysfunction from environmental causes by understanding how environmental factors, individual susceptibility, and age interrelate.

National Institutes of Health (NIH): One of eight health agencies of the Public Health Service (the Public Health Service is part of the U.S. Department of Health and Human Services). Composed of 24 separate institutes, centers, and divisions, NIH is the largest biomedical research facility in the world.

nontoxic: Not harmful or poisonous.

Office of Science Education (OSE): The Office of Science Education of the National Institutes of Health (NIH) coordinates science education activities at NIH and sponsors science education projects in-house.

organism: The highest level of cell organization. All organisms carry out life processes.

overdose: Too large a dose; a dose to excess.

A - E, F - O, P - Z