In an article published on November 14, 2016 by the Silent Spring Institute, Herb Susmann, data scientist and software developer at the institute, discusses the collective exposure of populations to toxic chemicals. “There are thousands of untested chemicals on the market, and every day we are exposed to potentially harmful chemicals in our environment and through the products we use,” Susmann states. While the impact of certain chemicals on an individual person’s health might be small, adding up all of the individual health impacts in the population may result in “a considerable negative impact on public health.”

Susmann illustrates this by using the example of polybrominated flame retardants (PBDEs), explaining that these chemicals can affect brain development and lead to a decreased IQ in children. “If you were looking at one child at a time, you may not notice the decrease in IQ since the loss is within the margin of error and could be easily dismissed,” Susmann elaborates. However, supposing that every child loses a few IQ points because of prenatal exposure to PDBEs, the bell-shaped curve of normally distributed IQs in a population would shift towards lower scores. Such a shift would increase the number of children with an intellectual disability (i.e. IQ below 70) dramatically.

Susmann notes that “this example is an over-simplification,” however it “illustrates the broader point that even very small reductions in individual people’s health can have a large impact on the overall health of the population,” he concludes.

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Herb Susmann (November 14, 2016). “It all adds up: Our collective exposure to toxic chemicals.