Page 385 - Environment: The Science Behind the Stories

regulations on packaging and advertising have helped to TAble 14.1 Selected environmental hazards
decrease cigarette use, warn the public of the risks of drugs
and alcohol, and advise us on issues of nutrition and exercise. Outdoor Air
Education on sex and reproductive health is helping women • Chemicals from automotive exhaust
avoid unwanted pregnancies and is slowing population growth • Chemicals from industrial pollution
(pp. 221, 224), and the promotion of condom use is helping to • Photochemical smog (p. 483)
slow the spread of HIV/AIDS (p. 227). • Pesticide drift
Such efforts are being spearheaded internationally by • Dust and particulate matter
the United Nations, the World Health Organization, the U.S. Water
Agency for International Development, and nongovernmental • Pesticide and herbicide runoff
organizations and funding agencies. Private foundations, such • Nitrates and fertilizer runoff
as the Bill and Melinda Gates Foundation, have been instru- • Mercury, arsenic, and other heavy metals in groundwater
mental in supporting health initiatives around the world. The and surface water
Gates Foundation alone has donated over $15 billion since
1994 to global health programs promoting disease prevention, Food
prenatal care for pregnant women, and enhanced food security. • Natural toxins
• Pesticide and herbicide residues
Toxicology is the study of chemical hazards Indoors
• Smoking and secondhand smoke
Although most indicators of human health are improving as • Radon
the world’s wealth increases, our modern society is exposing • Asbestos
us to more and more synthetic chemicals. Some of these sub- • Lead in paint and pipes
stances pose threats to human health, but figuring out which • Toxicants in plastics and consumer products (bisphenol A,
of them do—and how, and to what degree—is a complicated PBDEs, phthalates, etc.)
scientific endeavor. Toxicology is the science that examines the • Toxic compounds produced by mold
effects of poisonous substances on humans and other organ- • Dust and particulate matter
isms. Toxicologists assess and compare substances to deter-
mine their toxicity, the degree of harm a chemical substance
can inflict. A toxic substance, or poison, is called a toxicant, nations. Radon is a highly toxic radioactive gas that is color-
but any chemical substance may exert negative impacts if we less and undetectable without specialized kits. Radon seeps
ingest or expose ourselves to enough of it. Conversely, if the up from the ground in areas with certain types of bedrock and
quantity is small enough, a toxicant may pose no health risk can accumulate in basements and homes with poor air circu-
at all. These facts are often summarized in the catchphrase, lation (Figure 14.7). The EPA estimates that slightly less than
“The dose makes the poison.” In other words, a substance’s 1 person in 1000 may contract lung cancer as a result of a life-
toxicity depends not only on its chemical properties, but also time of radon exposure at average levels for U.S. homes, with
on its quantity. risks from radon varying according to a region’s underlying
In recent decades, our ability to produce new chemicals geology (see Figure. 17.33, p. 494 ). Another indoor hazard is
has expanded, concentrations of chemical contaminants in the asbestos. There are several types of asbestos, each of which
environment have increased, and public concern for health and is a mineral that forms long, thin, microscopic fibers. This
the environment have grown. These trends have driven the rise
of environmental toxicology, which deals specifically with
toxic substances that come from or are discharged into the
environment. Toxicologists generally focus on human health, Figure 14.7 People can determine their exposure to radon
using other organisms as models and test subjects. Environ- gas with in-home testing. Air samples are collected in special-
mental toxicologists study animals and plants to determine ized collectors like the one shown, and then mailed to a laboratory
the ecological impacts of toxic substances and to see whether for analysis.
other organisms—like canaries in a coal mine—can serve as
indicators of health threats that could soon affect people.

Many environmental health hazards
exist indoors

Modern Americans spend roughly 90% of their lives indoors.
Unfortunately, the spaces inside our homes and workplaces,
just like the outdoors, can be rife with environmental hazards
(TAble 14.1; see also pp. 493–496).
Cigarette smoke and radon are leading indoor hazards (p.
384 494) and are the top two causes of lung cancer in developed

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