How the Chemistry of Human Progress Became the Environment's Largest Problem

By: Dr. Adam J Gushgari, Senior Director – Emerging Contaminants, Eurofins Environment Testing USA

It could be argued that the human race has been one of the most behaviorally robust species to have ever existed, uniquely capable of adapting to many different environments through a combination of biological evolution, technological innovation, and cultural modification. The Toba Catastrophe Hypothesis suggests a human population bottleneck occurring around 75,000 years ago which reduced the global human population to between 3,000 and 10,000 individuals, and recent evidence surrounding the Early Pleistocene Bottleneck suggests ancestral human populations may have dropped to as few as 1,300 individuals around 850,000 years ago. While such near-extinction events would normally mark the end of a species, humanity has survived not one, but two of them (to our current knowledge!). Our current geologic epoch, the Holocene, has been characterized by a period of relatively stable climate that allowed human civilization to grow from a few million estimated individuals to over 8.2 billion people over the course of just 11,700 years.

Many scholars have argued that the age of the Holocene is actually behind us, and have urged acknowledgement of a new geologic epoch: The Anthropocene. Derived from the Greek words anthropos (human) and kainos (new), the term essentially denotes "the age of humans," a nod to the idea that human activity has become a considerable, if not the dominant force shaping the Earth's physical, chemical, and biological systems. While the purpose of my writing here today is not to take a stance for or against the formal acknowledgement of the Anthropocene, it is difficult to deny that humanity's presence on Earth has had a marked impact on it. Synthetic nitrogen fertilizer production, an invention that allowed the development of a food system capable of supporting billions of people, has also created the conditions for widespread eutrophication of freshwater and marine environments: massive algal blooms that deplete dissolved oxygen in surface waters, leading to large-scale die-offs of aquatic species. The construction of cities and mega-cities, which collectively house over 45% of the global population, has brought its own suite of consequences, from the urban heat island effect to the alteration of natural land cover. These phenomena share a common thread, and one that is likely to define the Anthropocene's mark on the geological record: the introduction of materials, compounds, and processes into Earth's systems at a scale and pace that the environment is fundamentally unequipped to manage.

The chemical contamination of freshwater resources and broader environments represents one of the most pervasive consequences of industrial growth. A 2020 peer-reviewed global chemical inventory identified over 350,000 chemicals and mixtures registered for commercial production and use worldwide. Of these, approximately 50,000 are designated as confidential business information, while an additional 70,000 remain inadequately characterized due to their nature as polymers, complex mixtures, or biological substances lacking a distinct chemical identity. While chemicals such as PCBs, DDT, PFAS, and select endocrine-disrupting compounds (EDCs) have been subject to regional and occasionally international bans, many resist environmental degradation and continue to impact both natural and built environments for decades following regulatory action.

Compounding this challenge is the largely unresolved complexity of chemical interactions once they enter the environment. Synergistic toxicity is a documented phenomenon in which the co-occurrence of two or more contaminants produces a toxic effect greater than the sum of the individual contaminants alone. To put it simply, certain chemical combinations can be far more dangerous together than either substance would be on its own. Transformation product toxicity occurs when two or more contaminants chemically react to produce a new compound that is more toxic than either of the original substances. Despite both phenomena being recognized in scientific literature, they receive remarkably little consideration in the development and regulatory review of new chemicals and industrial products. The documented occurrence of these interactions reveals a fundamental blind spot in how we assess chemical risk: with the possible combinations among 350,000 commercially produced chemicals being effectively limitless, and the existing regulatory framework built almost exclusively around evaluating individual contaminants in isolation, it is reasonable to conclude that current approaches are not merely incomplete but are structurally incapable of accounting for the chemical complexity present in real-world environments.

If you are in, or adjacent to, the field of environmental science, a few emerging contaminant classifications have likely crossed your radar. Per- and polyfluoroalkyl substances, or PFAS, are perhaps the most prominent. The same chemical traits that made PFAS attractive for inclusion in a wide variety of industrial and consumer products, namely their ability to simultaneously repel both water and fats, their resistance to heat and biological breakdown, and their low surface tension, coincidentally make them prime candidates for widespread environmental contamination and accumulation up the food chain in predator species. On the heels of PFAS is a renewed focus on micro- and nano-plastic contamination, which has been correlated with both direct negative health impacts and the potential for plastic particles to act as a vehicle for other hazardous compounds, effectively carrying chemical contaminants into organisms that ingest them. Endocrine-disrupting compounds represent a third major area of concern, with over 2,000 suspected EDCs currently circulating in natural and built environments. What makes this class particularly striking is that with EDCs, the dose does not make the poison. Significantly low concentrations, sometimes in the parts-per-trillion range, encountered at specific developmental windows have shown marked impacts on the hormonal system that can significantly decrease quality of life for the exposed individual, and some EDCs have demonstrated transgenerational impacts, with negative health implications observed in subsequent generations without any direct exposure to the substance.

Beyond these major classifications, a growing list of individual contaminants has drawn significant scientific attention due to their impacts on wildlife and human health, including pharmaceuticals and personal care products, nano-engineered materials, flame retardants, artificial sweeteners, pesticides, tire rubber chemicals, quaternary ammonium compounds, and disinfection byproducts. Two things quickly become clear: the issue of environmental chemical contamination has become both widespread and deeply significant, and the issue is incredibly complex. As the old adage goes, we cannot manage what we cannot measure.

Measurement and monitoring of environmental contaminants across air, water, and soils is essential in the effective management and remediation of these challenges. Robust environmental monitoring frameworks spanning passive sampling in aquatic systems, biomonitoring in sentinel species, atmospheric deposition monitoring, and advances in high-resolution mass spectrometry and non-targeted analytical screening are increasingly capable of detecting not just the contaminants we are actively looking for, but those we are not. This distinction is critical: the history of environmental contamination is largely a history of delayed recognition, where the consequences of chemical exposure became undeniable long before the scientific and regulatory infrastructure was prepared to act on them. DDT was in widespread use for over three decades before its ban. PFAS compounds were detected in human blood globally before a single enforceable drinking water standard existed. The pattern is both consistent and unacceptable.

The Anthropocene, if we are to accept it as our current chapter, will ultimately be defined not just by what humanity built, but by what it left behind. The chemicals we have introduced into Earth's systems, many of them invisible, poorly characterized, and resistant to degradation, represent one of the most enduring and consequential legacies of industrial civilization. Addressing this crisis will require more than incremental improvements to existing regulatory frameworks. It will require a fundamental shift toward proactive, systems-level environmental monitoring, international chemical transparency, and a precautionary approach to the introduction of new substances into environments that, as the evidence increasingly suggests, we do not yet fully understand.