Environmental Impacts of Emerging Contaminants

 

Ed. Ryan M. Colker and Robert D. Day

 

 

This executive summary reports the results of Renewable Natural Resources Foundation’s 2005 Congress on Environmental Impacts of Emerging Contaminants. Copies of the full report may be downloaded for free at http://www.rnrf.org. Permission to reprint has been granted by RNRF.

 

Introduction

 

Recent news accounts report the decline of amphibian populations worldwide, the feminization of male fish, and other disturbing trends. Our increasing use (and accompanying environmental releases) of various man-made compounds is suspected of contributing to these trends. No ecosystem is spared from potential effects from these compounds— flame retardants and other persistent anthropogenic compounds have been found even in the bloodstream of arctic polar bears. U.S. Geological Survey (USGS) scientists recently published data on the existence of contaminants in American streams. The scientists measured the concentrations of 95 organic wastewater contaminants in water samples from a network of 139 streams in 30 states representing multiple surrounding land uses. Contaminants were found in 80 percent of the streams sampled—with many samples containing multiple contaminants. Contaminants detected include steroids, nonprescription drugs, insect repellant, detergent metabolites, fire retardants, antibiotics, hormones, prescription drugs, and fragrances. For most of the compounds detected, there is no basis for limiting potentially harmful effects— water quality standards, drinking water standards, drinking water standards, maximum contaminant levels (MCLs) or other standards do not exist.

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Recognizing the pervasiveness of and the lack of knowledge about contaminants, directors of the Renewable Natural Resources Foundation (RNRF) called a national “Congress on Assessing and Mitigating Environmental Impacts of Emerging Contaminants.” Further, evidence of the increasing environmental impacts of these compounds made explicit the need for increased knowledge and understanding within the professional and scientific community. Thus, the congress brought together a select group of professionals from RNRF member organizations and leaders from government, industry, academia, and nongovernmental organizations (see Appendix A). Delegates met December 1–2, 2005, at the headquarters of the American Geophysical Union in Washington, D.C.

 

Specific goals of the congress were to raise awareness of emerging contaminants and their impacts, and to develop findings and recommendations through interdisciplinary discussion. To achieve these goals, the congress focused on the following objectives:

 

 

Following discussion of the objectives and background information (including four case studies) in plenary sessions, delegates were divided into small working groups. These working groups examined critical issues and possible solutions in greater depth. Findings and recommendations of congress delegates do not necessarily reflect policies and views of RNRF, its member organizations, or the sponsoring agencies.

 

Contaminants of Concern

Pesticides and Agrochemicals

By their very use, pesticides and other agrochemicals are introduced directly into the environment. Before the development of synthetic chemicals for the control of pests, compounds such as arsenic, lead, mercury, cyanide, creosote, and tars were used. These compounds posed significant threats to the environment. The introduction of chlorinated hydrocarbons was thought to be an improvement. However, their high chlorine content made many of them highly persistent in the environment. They can be very toxic to aquatic species and chronic toxicity problems have been observed, particularly in birds and mammals. The Environmental Protection Agency (EPA) recognized the need to regulate these persistent, lipophilic, bioaccumulative chlorinated hydrocarbons and to encourage the development of more biodegradable compounds. Concerns about carcinogenicity, groundwater contamination, and acute toxicity problems shaped the development of pesticides. Endocrine disruptors have become one of the more recent chemical classes of concern. As each new concern is raised, efforts are made to develop compounds to address to these concerns.

 

The synthetic pyrethroids provide an example of pesticide development, and are indicative of some of the concerns facing the environment (their development is described in the report). Several new classes of insecticides also have been developed. Some of them are very biodegradable and have mechanisms of action (MOAs) specifically targeted to insects; others are more persistent and have non-selective MOAs. New natural products also are being introduced into the market— many with highly selective MOAs. The use of pesticides, hormones, and other agrochemicals raises numerous concerns. How persistent are they? What are the transformation products? How bioavailable are they? How selective are their MOAs? What are the potential non-target effects (humans, wildlife, aquatic and marine species, invertebrates, microbial communities) associated with their use? Crops

 

Pharmaceuticals and Personal Care Products

Pharmaceuticals and personal care products (PPCPs) are a diverse group of chemicals comprising all human and veterinary drugs, diagnostic agents,

“nutraceuticals,” and other consumer chemicals such as fragrances, sunscreen agents, and excipients (“inert” ingredients in PPCP formulation and manufacturing). Thousands of distinct chemical entities in numerous (and increasing) therapeutic classes and end uses are considered PPCPs. Large numbers— by their very nature—are highly biologically active. In general, most are not regulated water pollutants.

 

PPCPs can enter the environment by a number of means. Domestic sewage is a major source. Portions of most ingested PPCPs are excreted primarily via urine and feces. The excreted PPCPs and derivatives can escape degradation in municipal sewage treatment facilities. The undegraded molecules then are discharged into receiving surface waters or groundwater.

 

Externally applied products that are not absorbed may be discharged directly to surface waters or to water treatment facilities as they are dislodged or washed off. Other potential routes include leaching from municipal landfills following disposal of unused products, the direct discharge of raw sewage, sewage discharge from cruise ships, runoff from confined animal feeding operations (CAFOs) and medicated pet excreta and other agricultural losses.

 

PPCPs detected in the USGS study include antibiotics, caffeine, pain relievers, antidepressants, and steroids.

 

The ramifications of PPCP introduction into the environment can be significant— particularly in the aquatic ecosystem. Any chemical that is introduced into aquatic ecosystems can lead to continual, multigenerational exposure for aquatic organisms. Even if the introduced compound easily biodegrades, the continual input from treated sewage may impart PPCPs with “pseudo-persistence.” The impacts of PPCPs in the environment on nonaquatic species are largely unknown, particularly when present in mixtures or at low concentrations. The potential for subtle effects raises serious concerns.

 

Industrial and Household Chemicals

The production and use of industrial chemicals have long been associated with society’s desire to improve life. However, some of these chemicals have proven to be harmful to human, ecosystem, and wildlife health (e.g., asbestos, PCBs, and dioxins). One group of compounds of increasing concern is the brominated flame retardants.

 

As increasing amounts of construction materials, furniture, and appliances were being made of plastic, concerns regarding the danger of fire, rapid ignition, fast flash-over times, and the spread of fire grew. Flame retardants were introduced into the products to mitigate some of these concerns. Because of their high efficiency and low cost, brominated flame retardants use has surpassed the use of other flame retardants. These chemicals appear in significant quantities of consumer products including electronics, carpeting, and foam containing products such as mattresses, car upholstery, and furniture.

 

The structures of some PBDE (a type of brominated flame retardant) metabolites are similar to the thyroid hormonethyroxine (T4), and some forms may disrupt the endocrine system. EPA scientists and other researchers expect that certain PBDE congeners likely are carcinogens, induce liver enzymes, may affect neurological, developmental, and reproductive systems, and likely are endocrine disruptors. Mammalian toxicity studies have shown decreases in thyroid hormones T4 and T3, delayed onset of puberty in female offspring, developmental neurotoxicity in mice, and neoplastic nodules in the livers of rats.

 

Understanding how PBDEs enter the environment is crucial for efforts to minimize exposure to both humans and wildlife. Potential sources include

PBDE or polymer production sites, releases from products during use, and disposal or recycling of used products. Some of these compounds, which are ubiquitous in the U.S., have been banned in Europe. Several states have taken the lead in regulatory efforts to ban or limit the use of certain PBDEs.

 

Nanomaterials

Nanotechnology has been touted as the next industrial revolution. Yet, significant unknowns have raised concerns about potential releases into the environment and the impacts on human, ecosystem, and wildlife health. A vast number of nanoparticles are new chemical forms of common chemical elements. Because of their size, nanomaterials exhibit unique mechanical, electronic, photonic, and magnetic properties that may differ greatly from macroscopic versions of the same compounds.

 

Nanoparticles already appear in many consumer products, including cosmetics, sunscreens, wrinkle-free clothing, and food. High technology products also are being introduced.

 

As the quantity of nanomaterials introduced into the environment continues to skyrocket, concerns have been raised about the potential impacts on human health and the environment. The ability to image, measure, model, and manipulate matter on the nanoscale to exploit new properties and functions presents significant challenges, not only for the materials scientist, but also for those who seek to monitor and assess the effects of nanoparticles in the environment. Far less effort has gone into determining potential effects, although EPA and others have begun to support this kind of research. Preliminary studies have shown that these particles have the ability to enter vital organs including the brain.

 

Traditional methods of monitoring toxicity and dose concentrations would not be appropriate. Measuring effects presents additional challenges since the toxicological literature on nanoparticles currently is so limited. Once these materials enter the environment, they are not easily detected and no effective clean-up methods exist.

 

The ability of federal agencies to adequately regulate nanomaterials has been a subject of concern by many. Agencies believe they have the ability to regulate these materials under existing statutes. Many delegates expressed doubts about that, and had significant concerns about the numerous unknowns associated with nanotechnology.

 

Findings and Recommendations

Monitoring Needs

Measuring the effectiveness of regulatory activities and focusing research on topics of greatest concern is essential to the efficient use of limited resources.

Environmental monitoring helps provide these measurements and this focus, yet, it chronically suffers from inadequate funding. Monitoring is useful in identifying the extent of contamination or identifying new potential contaminants of concern. It provides the vital function of helping determine if regulatory controls have adequately protected human health and the environment.

 

 

Research Needs

Monitoring and research are complementary. As monitoring reveals the extent and effects of contaminants in the environment, research is necessary to determine the implications of such information. Additionally, understanding the fate, toxicity, and MOAs of compounds is critical to streamlining the regulatory process and predicting future compounds of concern.

 

 

Regulatory Issues

Regulations are designed to protect society’s interests either directly by prohibiting unwanted behavior or effects, or indirectly by encouraging a particular outcome through market forces, competition, or other means. Working-group members examined direct and indirect means to protect human health and the environment from unintended consequences of the use of chemicals.

 

 

Public and Professional Education Issues

A public that is educated about contaminant issues will increase the likelihood of having informed public policy and actions. Support for research and monitoring will increase as the public comes to better understand the many unknowns surrounding chemicals. Public support also will increase with knowledge of risks to human and ecological health.