More precise techniques to evaluate chemical safety are under development, including mechanistic studies to illuminate exactly what changes a chemical exerts within a cell. Such methods, however, tend to be time-consuming and expensive and thus are not widely applicable in large-scale studies (143).
Meanwhile, policymakers must rely on the best available data – often from animal studies and risk assessments – in setting policies to protect the public from suspected risks. Because chemical products are so widely used and evidence suggests they may damage the environment and human health, governments face increasing pressure to adopt the “precautionary principle.” This principle affirms that when harm is strongly suspected, it is best to take action to prevent exposure, even if absolute proof of harm is missing.
Such prudent policies are by no means the norm. As described in more detail in Changing Environments, Changing Health, many chemicals banned in developed countries are still in widespread use throughout the developing world, despite their known hazards, because they are cheap and effective. Among them is a class of particularly hazardous products known as persistent organic pollutants, or POPs. Similarly, roughly two decades after the United States began to phase out the use of lead in gasoline because of its well-known health effects, it remains ubiquitous throughout much of Asia and Latin America.
Efforts to minimize pollutants’ harmful impacts are complicated by the increasing realization that they can harm human health not just through direct toxicological routes but also indirectly, through large-scale ecological disruptions. This realization hit home with the unexpected discovery in 1985 of a “hole” in the stratospheric ozone layer, caused by human activity leading to chlorofluorocarbon emissions (144). The health impacts of this thinning ozone layer, which protects the Earth from harmful ultraviolet radiation, range from skin cancer to cataracts to immune system depression to disruption of the food chain. None of these results was anticipated a mere 15 years ago. Similarly, the combustion of fossil fuels not only causes urban air pollution but also disrupts atmospheric chemistry and may lead to global warming. Plausible health impacts include increased deaths from excessive heat episodes and violent storms, and a greater toll from malaria and other vector-borne diseases in developing countries.
References and notes
143. D. Briggs, C. Corval