Stressor Exposures Determine Risk: So, Why Do Fellow Scientists Continue To Focus on Superficial Microplastics Risk?

A couple of years ago, I tried to publish an Op-Ed challenging the perceived environmental threat of microplastics in the New York Times, Washington Post, LA Times, Chicago Times, and Wall Street Journalbut these respected news outlets rejected my submission. Subsequently, I published a Letter to the Editor in the journal Integrated Environmental Assessment & Management. This did little to change the concern expressed here. The focus on my opinion article was the concern that the environmental risk from microplastics (more specifically, microbeads) was overstated. As an environmental toxicologist and risk assessor, I knew low microplastic exposure concentrations dictated there could be no risk. Thankfully, others are now beginning to join this chorus. Even when scientific knowledge was in its infancy, Paracelsus stated in ∼500 AD a currently held, toxicological truth: All things are poisons at the right dose.My concern that microplastics in marine and freshwater ecosystems aquatic environment are not a risk due to LOW concentrations (i.e., low exposures) is slowly being realized and certainly applies to other contaminants of emerging concern. Recently, an Environmental Science & Technology Viewpoint article by Wiltje and Sumpter challenged scientists to better define environmentally relevant concentrations as all too often this term is loosely used. Numerous authors and organizations have called for standardized methods for collecting, quantifying, and characterizing microplastics. A plethora of methods exist for each of these three critical components of environmental assessments, each with their own strengths and limitations, but no one is sufficient. High numbers of false positive and false negatives have been identified, depending on the methods used, which makes it impossible to compare microplastic studies that may be overestimating or under-estimating exposures. Nevertheless, the great majority of studies are stating the highest concentrations typically found are in the range of less than 1 to 10s of particles per meter squared (i.e., 1000 L). These concentrations are several orders of magnitude lower than virtually all laboratory studies and organisms feeding on this sized range will find orders of magnitude more plankton available for ingesting. Also, many of the studies measure concentrations based on mass (e.g., mg/L) or surface area (number/km), and these units add large uncertainty to actual organism exposures to these diverse particles. As Editor-in-Chief of one of the premier journals for environmental toxicology, I find the continuing publication of microplastics studies stating a severe environmental threat, in high quality journals disturbing. These studies are rapidly picked up by the news media, as we have seen and serve to misinform the public and policy makers, as noted by others. Are reviewers and Associate Editors for our highest quality journals simply unaware of what constitutes hazard and risk and how exposure is the most important part of the equation? Since scientists should be nonbiased, how can this be happening? Is the penchant for visibility, pressure to publish, inability to publish negative results, funding, and sensationalism overtaken this science? This seems unethical. In the Environmental Science & Technology Feature by Koelmans et al., they present a comprehensive coverage of these issues and propose and simple and eloquent path forward. In my opinion, this trend of reporting has adversely influenced policy making (e.g., the banning of microbeads one of the lesser components of microplastics and clearly not an environmental threat). The dominant component of microplastics characterized to date are not microbeads, rather polyester fibers or fragments (depending on which study cited), which are also below concentrations causing adverse effects. Nevertheless, there is no call by environmental advocates to ban polyester clothing or to ban all plastics which eventually will disintegrate to fragments. Colleagues in the industries affected by this ban have said privately at international scientific conferences it is a battle their respective companies have chosen not to fight. Well, that is wonderful, fewer microbeads being dischargedbut if there was no adverse exposure to begin withwhy care?