From an epidemiological perspective, why are chronic and pervasive environmental toxicological exposures so difficult to investigate? What factors make these types of exposures difficult to assess, and what makes it so difficult to establish patterns of exposure when the exposure is pervasive in the environment and chronic over a period of time? What methods might an epidemiologist use to try to collect data on this type of exposure?
As an epidemiologist, some of your goals when presented with exposure to a toxic element are to determine the source of the toxin, the number of people exposed, the number of people who become ill, and how to limit further exposure. When a toxin in the environment is pervasive and people are chronically exposed, the epidemiologist's task is made extremely difficult. For example, if an illness appears among a group of people and it is determined that they only have one thing in common, such as all receiving drinking water from the same water supply, the epidemiologist can locate this water supply and, using symptoms and dates that people became ill, possibly pinpoint the exact date when contamination of the water supply occurred. The same kind of tracking can be done with food poisoning outbreaks by a process of elimination: it is necessary to exhaustively review everything each person ate and narrow down the one item they all have in common (for example, cases have been linked to everything from spoiled potato salad to contaminated raspberries from Central America).
Discusses the factors that complicate epidemiological investigation of chronic and pervasive exposures to environmental toxins. Provides reference to Centers for Disease Control epidemiological resource on tracking of environmental exposures.