Nov 16, 2020 in Health

Environmental Epidemiology assessment

Environmental Epidemiology Assessment

According to the generally accepted definition, environmental epidemiology is the study of distribution and determinants of health-related states or events in specified populations that are influenced by physical, chemical, biological, and psychological factors in the environment (Merrill, 2009). In other words, environmental epidemiology investigates the interrelationship between the distribution of human health and disease on the one hand and the exposure to environmental agents on the other. In other words, a natural experiment is an unplanned, naturally occurring kind of cohort study aimed at establishing the effects of the natural incident. Interestingly, natural experiments liquidate many problems attending the performance of laboratory and field experiments (Halperin & Heath, 2012). Descriptive epidemiology is the most prevalent type of epidemiological research. According to Merrill (2011), descriptive epidemiology is used to assess and monitor the health of communities and to identify health problems and priorities according to person, place and time factors (p. 43). Descriptive epidemiologists seek to answer the question of how a specific health problem is distributed among the concerned populations (Cwikel, 2006, p. 185). The odds ratio is an adequate estimate of what the relative risk could be. According to Susser, Schwartz, Morabia & Bromet (2006), the disease odds ratio is the odds of disease in the exposed divided by the odds of disease in the unexposed (p. 77). Relative risk is the ratio of two risks, which indicates the degree of risk.


John Snow is widely considered to be the patriarch of modern epidemiology. He made his first discreet forays into epidemiology in the early 1850s, when he made a battery of groundbreaking natural experiments on cholera outbreak in London. Using Snows own words, it would be fair to mention that the second experiment was astonishing in its size:

No fewer than three hundred thousand people of both sexes, of every age and occupation, and of every rank and station, from gentlefolks down to the very poor, were divided into two groups without their choice, and, in most cases, without their knowledge (cited in Bookstein, 2014, p. 122).

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One group of people was exposed to water containing raw sewage, while the other had an access to pure potable water. Snows work was a veritable natural experiment, because the Londoners were allocated into two groups by natural circumstances rather than by the whim of the experimentalist. Nevertheless, Snow had availed himself of this natural occurrence and tested his conjecture. The epidemiologist relied on the classic experimental design in order to dissect the collected data and draw conclusions for the eventual eradication of cholera.

Out of all the reasons that make epidemiology an essential scientific field, its ability to help disease detectives to get to the root of health problems in a community stands out as the most important. Likewise, epidemiological research may assist scientists in figuring out how to prevent outbreaks of dangerous pandemics sweeping through the environment. By investigating how people become sick, epidemiologists provide an invaluable service to humankind, thereby helping to shield communities from health issues in the future. Rushton & Elliott (2003) argue that epidemiological research is observational rather than experimental in design and has a number of limitations, especially where access risks of any adverse health effect are small, as will be the case with most environmental exposures encountered today in the developed world.

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The study of long-term health effects of air pollution relies heavily on ecologic analysis. The analysis is usually conducted through the instrumentality of either cross-sectional or cohort studies, wherein ecologically assigned exposure is employed. Foremost among the factors that may affect ecological study results are exposure misclassification and the use of a limited number of study areas.

Friis (2012) argues that Percivall Potts observations constitute the foundation stone of cancer prevention. Indeed, Pott was the first to have vindicated the existence of links between cancerous malignancies and environmental carcinogens. He made an indisputable contribution to the epidemiological science insomuch that his investigations led to the adoption of the Chimney Sweepers Act 1788. The act outlawed employment of little children in particularly hazardous environments, where they became liable to noisome, painful and fatal diseases (Friis, 2012).

Hills criteria for disease causation, developed by the eponymous British statistician, outline the minimal conditions necessary to establish a causal link between a specific factor and a disease. The criteria set forth by Bradford Hill range from strength, consistency, specificity, temporality, plausibility and coherence to biological gradient, experiment and analogy.

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The epidemiological triangle is a common model designed to study health problems insomuch that it helps researchers to understand the whys and wherefores of the spread of infectious diseases. Similarly, it illustrates the relationship among an agent, i.e. a microbe that causes the disease, a host, i.e. an organism harboring the disease, and the environment, i.e. external factors enabling disease transmission. The model applies to biological, chemical and physical agents.

With a view to explaining the distribution of disease incidence and identifying strategies of disease prevention, descriptive and analytical research designs are used most often in epidemiology. In stark contrast to descriptive studies, which attempt to answer the what question, analytical studies deal with why questions. Whereas descriptive studies describe data on health outcomes, analytical epidemiology describes the reasons behind the occurrence under scrutiny.


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