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“Emerging” Chemicals As Pollutants in the Environment: a 21St Century Perspective

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“Emerging” Chemicals As Pollutants in the Environment: a 21St Century Perspective “Emerging” Chemicals as Pollutants in the Environment: a 21st Century Perspective Christian G. Daughton Editor's Note—Pesticides, pharma- RNRF’s upcoming Congress on Assess- taminants are regulated under interna- ceuticals, industrial chemicals, ing and Mitigating Environmental Im- tional, federal, and state programs, nanoparticles, and personal care prod- pacts of Emerging Contaminants, these represent but a minuscule frac- ucts are being detected increasingly scheduled for December 1-2, 2005, in tion of the universe of chemicals that throughout the environment. These sub- Washington, D.C. occur in the environment as a result of stances are being detected in tissues both natural processes and human ac- of humans, terrestrial animals, amphib- Abstract tivities. This array of chemical pollut- ians, and fish. We believe that a basic ants (or occupational hazards) might understanding of existing and poten- Defying comprehension is the com- at first seem large, but it pales com- tial threats posed by these substances plexity of the chemical sea that sur- pared with the universe of known has become prerequisite knowledge for rounds, sustains, and constitutes all life. chemicals, and would become insig- natural resources managers, profes- From this sea, never-ending challenges nificant if compared with those chemi- sionals in related disciplines, and those are faced by organisms striving to de- cals yet-to-be identified, waiting to be in government whose decisions affect fend against those multitudes of chemi- synthesized, and that are just now monitoring and regulatory activities. cals that cause cellular stress or harm. “emerging.” A key assumption is im- Thus, we have dedicated this issue of Biological mechanisms have evolved plicit in the limited and selective lists the Renewable Resources Journal to an for maintaining organism homeostasis or menus of chemicals targeted by expansive overview of the extent and during contact with these harmful sub- regulations—namely that these are in- nature of challenges we face. The next stances. Most of these chemical stres- deed the chemicals responsible for the issue of our journal will extend the ex- sors have long existed or are produced most significant share of risk to eco- amination by presenting findings and by myriads of human activities. How- logical integrity, economic impair- recommendations stemming from ever, for those chemicals that are rela- ment, and human health. Given the tively new to the world, the mecha- myriads of other chemicals that are nisms for homeostasis maintenance are ignored or escape notice by regulatory Daughton is chief, Environmental not necessarily adequate. Chemicals processes, a multitude of questions can Chemistry Branch, U.S. Environmen- for which organisms have had the least be posed regarding society’s relation- tal Protection Agency. This article has time to adapt are those that only re- ship with chemical pollutants, particu- been subjected to peer review. The cently have emerged as environmental larly with respect to whether a more United States Environmental Protec- contaminants. holistic understanding of risk might be tion Agency through its Office of Re- Essentially limitless combinations of required. With the immense size of the search and Development funded and a very small set of atomic elements can chemical universe, this is a daunting managed the research described here. yield a seemingly infinite number of challenge. How would we know when It has been subjected to the agency’s unique chemicals—a universe known we have narrowed the chemical uni- administrative review and approved for as “chemical space.” Although thou- verse to the most significant hazards publication as an EPA document. sands of chemical pollutants or con- worthy of our attention? Not necessar- 6 renewable Resources Journal Winter 2005 ily will the continued emergence of and its ramifications. More emphasis elucidated but which have long been new pollutants pose the biggest chal- needs to be placed on non-regulated present. There are a number of differ- lenge. A larger unknown might be the pollutants, especially those considered ent perspectives from which to view the occurrence of myriads of chemicals to be “emerging.” Over the last few many dimensions of “emerging” that remain hidden from our view. Per- years, the appellation “emerging” has (Daughton, comp. 2005a). One ex- haps more daunting will be gaining a been applied to chemical pollutants ample is that of PPCPs (pharmaceuti- better understanding of the unantici- with such frequency that its meaning cals and personal care products; see pated ways in which these substances is becoming confused. In reality, those Daughton, comp. 2005b), which in- can interact with the environment and pollutants that are truly “emerging” clude many substances that long have the creation of a new paradigm for their (for example, those that have just been present in the environment but management or stewardship. Adding gained entry to the environment be- whose presence and significance only yet additional challenge is the emerg- cause they are new to commerce) are now are beginning to be elucidated. ing realization that society is averse to sometimes confused with those whose “Emerging” also sometimes is intended exposure to certain chemicals, even in environmental presence just has been not to refer to the pollutant itself, but the absence of any hazard, simply be- cause these chemicals occur where they Table 1. Some Groupings of Chemical Pollutants. are not expected or desired—the chemical equivalent of “weeds.” Confusion results from their intersections and acronyms. Outlined in this paper is a sampling G:rouping Grouped According to of some of the many alternative per- spectives regarding chemical pollutants (especially those that are new to our EDC (Endocrine Disrupting Chemical) toxicological mode of action or attention—the so-called “emerging” endpoint pollutants) and their ramifications for CMR (Carcinogenic, Mutagenic, toxic biological systems and society’s val- to Reproduction) ues. A primary objective in presenting PBT (Persistent, Bioaccumulative environmental properties these alternative views of chemical pol- Toxic) (e.g., ease of degradation or fat lution is the hope of catalyzing dialog solubility) and debate regarding new approaches vPvB (very Persistent, very for its management, not to make rec- Bioaccumulative) ommendations for implementing solu- tions. POP (Persistent Organic Pollutant) Introduction PPCPs (pharmaceuticals type of intended usage and personal care products) Tremendous investments continue to be made in the prevention, control, and “priority pollutants,” legislative enactment mitigation of environmental pollution and other regulated pollutants (e.g., CERCLA) by chemicals. Nevertheless, how can we be sure that these are the most im- xenobiotics, exotics foreign versus endogenous portant chemicals with respect to pro- tecting humans and the ecology? Do we sufficiently understand the pro- toxicants, toxins, toxics overall toxicity (note: “toxins” are a cesses that dictate exposure to these special subset that are proteins; pollutants and its aftermath? Is the in- “toxics” is jargon for “toxicants”) troduction of new chemicals to com- “emerging” contaminants/pollutants novelty, fad, timeliness, or new merce outrunning our ability to fully concern assess their significance in the environ- ment or to human health? HPV (high production volume quantity (manufactured/imported in This article is intended to foster dis- chemicals) U.S. in annual amounts >1 million cussion aimed at establishing a more pounds) holistic view of xenobiotic exposure Winter 2005 renewable Resources Journal 7 rather to a newly hypothesized concern out the course of life on Earth. Some process, which takes place under con- regarding an old pollutant. For ex- are inherently harmful, some are essen- tinually changing conditions. Expo- ample, pollutants that long have occu- tial for sustaining life, and others share sure, for example, can range from pied our attention can gain new noto- both characteristics depending on their short-term contact with a small, select riety with the revelation of new aspects concentrations or when exposure oc- group of chemical stressors (“toxi- of their occurrence, fate, or effects; the curs during the course of an organism’s cants”) at relatively high concentra- production of acrylamide during the development or natural rhythms. Ex- tions (acute exposure), to extended cooking of certain foods is but one ex- posure, however, is not sufficient for durations of exposure with lower con- ample. toxicity. All organisms have evolved a centrations (chronic) of multitudes of A source of on-going confusion is complex repertoire of defense mecha- chemicals in extraordinarily complex the proliferation of acronyms for the nisms for coping with exposure to those mixtures. Effects can range from overt, different categorizations of chemical chemicals foreign to their normal ex- where adverse consequences are elic- pollutants. Various groupings of chemi- istence (xenobiotics). Living systems ited quickly (e.g., from a lethal dose), cal pollutants (see Table 1) have have developed protective, defensive, to subtle, where effects are not readily evolved, and each looks at chemicals or adaptive mechanisms for minimiz- apparent or easily measured (e.g., from a different perspective. Each ing exposure or even the toxicity of slight but gradual shifts in mental group tends to contain some but not many of the otherwise harmful,
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