Canadian Environmental Health Atlas

Understanding Our Environment is Key to Promoting Health and Preventing Disease

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Historically, scientists have relied on indirect methods to measure the effects of environmental contaminants on human health. These methods have included surveying community members using questionnaires and monitoring water and air quality.1Increasingly, health researchers are using biomarkers of industrial pollutants or environmental contaminants to directly measure exposures. Today biomarkers are also being used to examine the effects of exposure to contaminants and the susceptibility of individuals to particular contaminants.23

In the past, the effects of environmental contaminants on health were not appreciated until toxic substances had accumulated in the human body in sufficient quantities to cause obvious signs or symptoms (Figure 1). Indeed, most toxic substances were only recognized after widespread environmental exposure led to acute poisonings.4Still, serious health consequences—including premature death—can occur from low-level, chronic exposure because the adverse effects of environmental contaminants on human health are often insidious.

A variety of toxic chemicals and compounds that are widely dispersed in the environment can readily be found in the body fluids and tissues of many people.5Although the impairments caused by exposure to environmental contaminants can be subtle for an individual—for example, an increase in behaviours related to ADHD (attention deficit hyperactivity disorder)—the damage can be substantial at the population level (video), especially when an exposure is common.6

Studying Environmental Contaminants
Studying the adverse effects of chronic, low-level exposure to environmental contaminants is difficult because of substantial variability in the uptake and effects of toxic chemicals and compounds. This variability can be caused by differences in individuals’ genetic susceptibility, enzyme activity, and nutritional status.2

Unlike much clinical research, which relies on randomized controlled trials, the study of environmental contaminants and their effects has relied almost entirely on observational studies and the study of how laboratory animals react to contaminants. Increasingly, researchers are using biological markers, or biomarkers, to directly measure the actual levels or “dose” of substances in body fluids and tissue and link these exposures with disability or disease.127

  • 1. a. b. Sexton K, Needham LL, Pirkle JL. Human biomonitoring of environmental chemicals. American Scientist. 2004;92:38-45.
  • 2. a. b. c. Perera FP. Environment and cancer: who are susceptible? Science. 1997; 278:1068-1073.
  • 3. Lanphear BP, Bearer CF. Biomarkers in paediatric research and clinical practice. Arch Dis Child. 2005;90:594-600.
  • 4. Rogan WJ. Environmental poisoning of children: lessons from the past. Environ Health Persp. 1995;103 (Suppl 6):19-23.
  • 5. Landrigan PJ, Carlson JE, Bearer CF, et al. Children’s health and the environment: A new agenda for prevention research. Environ Health Perspect. 1998;106 (Suppl 3):787-794.
  • 6. Rose, G. The strategy of preventive medicine. Oxford University Press, 1992, Oxford, England.
  • 7. Centers for Disease Control. Second National Report on Human Exposure to Environmental Chemicals. U.S. Public Health Service, Department of Health and Human Services. 2003.