In the real world, no one is exposed to individual polycyclic aromatic hydrocarbon (PAH) compounds, but individual PAHs are arguably the most studies chemicals in toxicology labs. In the real world, everyone is exposed all the time and everywhere to materials that contain a mixture of PAHs, and those materials are also well studied, not just in laboratories, but in the environment and the workplace and medical clinics. This is why, in its 2014 chemical assessment work plan update the USEPA stated: “EPA believes [individual] PAHs should be assessed as a category rather than as individual chemical substances.
Because they have been thoroughly tested, studied and analyzed, the risks thought to be associated with exposures to PAH-containing materials are understood by the scientific community. Those risks are low -- whether evaluated from the point of view of real world exposures, such as happens in the workplace, or from the perspective of studies of laboratory animals exposed to individual PAHs. This is illustrated by Health Canada’s finding (see article in October 2016 issue) that, even when using exaggerated data generated by activist scientists at the US Geological Survey, risks associated with PAHs in house dust fall well below levels identified as “of concern for public health” by the World Health Organization and the European Food Safety Agency.
So the question has to be asked, Why are politicians in local governments in places such as Highland Park, Illinois, and Ann Arbor, Michigan, and San Antonio, Texas, so concerned about PAHs and materials that contain PAHs? One reason seems to be their reliance on the false claims by pro-sealant ban activists that PAH-containing materials haven’t been tested – they have both in the real world, where dozens of studies have shown little or no excess risk to workers exposed to PAH-containing materials, low bioavailability to animals in the environment, and low lifetime risks in bioassays conducted in experimental laboratory animals. Another reason is misapplication of the precautionary principle. The precautionary principle is a philosophical tool that some believe should be used to err on the side of caution when there are unknowns that create uncertainty in scientific understanding. However, when it comes to assessing risks associated with environmental exposures to PAH-containing materials, there is a high level of confidence that risks are low for both people and aquatic organisms. Where there is a high level of uncertainty in scientific understanding, however, is among local politicians and activists who are unequipped (because they lack the funding and scientific expertise) to evaluate the science. So the science is well established, but pro-ban advocates and the politicians acting on their advocacy don’t understand the science, creating high levels of personal uncertainty among non-experts. Combine that with a surprising willingness to act without evidence and, voila!, the precautionary principle is invoked.
Citizens and businesses should listen closely - when a politician says an action needs to be taken because of the precautionary principle, what is really at stake is something the politician wants to do but can’t find a fact-based reason for acting. In the case of local bans of RTS, the idea is presented by environmental activists as a common sense way to protect our health and environment when risks are unclear and the science is highly uncertain. What is actually on display is that the politicians and activists don’t understand what science knows about materials that contain PAHs. Their lack of understanding makes their assessment of risk highly uncertain.
