Coastal and Estuarine Risk Assessment - Chapter 3 ppsx

©2002 CRC Press LLC

Emerging Contaminants

of Concern in Coastal and

Estuarine Environments

Robert C. Hale and Mark J. La Guardia

CONTENTS

3.1 Introduction

3.2 Brominated Fire Retardants

3.3 Polychlorinated Biphenyls

3.4 Natural and Synthetic Estrogens

3.5 Alkylphenol Ethoxylates and Associated Degradation Products

3.6 Other Pharmaceuticals

3.7 Nonpharmaceutical Antimicrobial Agents

3.8 Personal Care Products

3.9 Interaction of Multiple Stressors

3.9.1 Multiple Xenobiotic Resistance

3.9.2 STP Sludge

3.10 Conclusions

Acknowledgments

References

3.1 INTRODUCTION

Coastal and estuarine areas are strategically located, serving as focal points for

commerce, as well as homes to a disproportionate share of the human population.

As a consequence, they also receive a disproportionate share of the contaminants

released. Because of their locations and their physical and chemical characteristics,

they may also receive and trap additional contributions from upgradient watersheds

and air sheds. Thus, these systems may be more vulnerable to degradation than less

dynamic environments. Despite this, coastal and estuarine areas are very important

wildlife habitats, serving as refuges and nurseries for a variety of organisms.

The initial and perhaps most important step in risk assessment, regardless of the

system, is problem identification (see Chapter 1 for a discussion of the elements of

3

©2002 CRC Press LLC

risk assessment). Ideally, identification of environmentally problematic chemicals

should be done prior to the occurrence of significant environmental damage. In

practice, this process is often reactive, occurring after deleterious impacts of signif￾icant magnitude have already occurred. Chemicals that have emerged as problems

in the past include organochlorine pesticides (e.g., effects on reproductive success

of piscivorous birds and deformities in reptiles), mercury (e.g., accumulation in

coastal marine life and resulting Minamata disease in Japanese residents), polybro￾minated biphenyls (e.g., PBB contamination of Michigan livestock and subsequent

transfer to humans), tributytin (e.g., mortality and reproductive problems in European

coastal shellfish), and Kepone (e.g., neurological disorders in Virginia chemical

workers and contamination of estuarine biota of the tidal James River).1–6 The time

lapse between initial introduction of contaminants and assessment of impacts is

critical, particularly when chemicals are resistant to degradation, are continuously

introduced, or are widely dispersed. In some cases remediation is not possible or

may be more destructive to the site than the contaminants themselves. Often chemical

monitoring efforts, capable of detecting the presence of many contaminants prior to

expression of widespread impacts, are retrospective and focus on so-called priority

or historical pollutants.7 Ironically, the justification offered in defense of this modus

operandi is often that monitoring lists should not be expanded as current monitoring

studies have failed to detect the compound in question. Analytical approaches also

are increasingly specific, which is an asset when highly accurate results for selected

chemicals at low environmental concentrations are required. However, this advantage

may prevent recognition of the presence of new problem chemicals in the environ￾ment.8 Deleterious effects are a culmination of all the chemicals (as well as other

stressors) to which organisms are exposed, not just those chosen for study or regu￾lation. We also are still learning what constitutes a significant effect. These effects

may range from acute mortality to reallocation of valuable energy or other reserves.

Chemicals of concern are those for which the combination of toxicity and

exposure exceeds a critical value, resulting in the expression of a deleterious effect.

An emerging chemical of concern may be one that has been released into the

environment for a considerable time, but for which effects have only now been

recognized. The exact number of chemicals actually in commerce is uncertain, but

estimates range as high as 100,000, with up to 1000 new compounds released each

year.9,10 The toxicological and environmental properties of only a fraction of these

have been examined. An emerging contaminant of concern may also be a preexisting

chemical whose production has increased, or for which a new use or mode of disposal

has been found, increasing exposure. Existing chemicals for which important new

modes of toxicity or environmentally important degradation intermediates have been

discovered also may merit attention.

Persistent chemicals tend to accumulate in the environment, resulting in height￾ened ambient concentrations and exposure.11 Bioaccumulative chemicals effectively

increase the dosage within organisms themselves, although the location of these

burdens may not coincide with the site of action. The impacts of so-called PBT

(persistent, bioaccumulative, and toxic) chemicals have been recognized. The sci￾entific literature is replete with studies on a few classes of these, notably polychlo￾rinated biphenyls (PCBs), organochlorine pesticides, and polycyclic aromatic

©2002 CRC Press LLC

hydrocarbons. In fact, the U.S. EPA has recently established a PBT initiative in its

Office of Pollution Prevention and Toxics. A significant portion of the emphasis

has again been on organochlorine chemicals, banned in most developed countries.

Mussel-watch data suggest that concentrations of these in U.S. coastal shellfish are

decreasing.12,13 Similar trends have been seen for organochlorines in other organ￾isms such as Canadian seabirds.14 While production of PCBs has stopped, large

amounts remain in service and residues continue to be redistributed in the environ￾ment. Some organochlorine pesticides also remain in use, particularly in the tropics,

on account of their effectiveness against disease-carrying insects and low cost.

However, because of their physical properties, organochlorines continue to be

transported to high latitudes, condense there, and accumulate in indigenous organ￾isms. There they pose threats even to indigenous human populations that have never

used the chemicals.15,16 These “transboundary” contaminants have justifiably

attracted the attention of the international scientific community, and efforts are

expanding to elucidate their fate and consequences.

In contrast, the vast majority of chemicals released have received comparatively

little attention from regulatory agencies and environmental scientists. A wider effort

is needed to identify emerging contaminants of concern. While not exhaustive,

several classes of these will be discussed here. Emphasis is on those that are

bioaccumulative, have atypical degradation pathways, or interact with biological

functions historically not fully considered by risk assessors.

3.2 BROMINATED FIRE RETARDANTS

Although we have learned much regarding designing chemicals with less deleterious

environmental properties, some PBT chemicals are still being manufactured and

used in large amounts. For example, a new generation of brominated fire retardants

apparently has filled the niche formerly occupied by PBBs, largely deposited fol￾lowing the Michigan livestock feed incident. Fire retardants may be additive (present

in, but not chemically bound to, the matrix) or reactive (covalently bound to the

matrix). Tetrabromobisphenol A is one of the most widely used brominated fire

retardants. It is reactive, limiting its dispersal somewhat. In addition, it has a log

Kow of 4.5; hence, its bioaccumulation potential is moderate.17

In contrast, brominated diphenyl ethers (BDEs) are additive fire retardants (see

Figure 3.1A for a representative structure). BDEs are particularly important emerg￾ing contaminants as a result of their PBT properties. They are widely used in

flammable polymers and textiles.18 Their role there is critical, substantially

decreasing the number of associated human fatalities. BDEs were first reported in

soil and sediment in the United States in 1979 near manufacturing facilities and

in a Swedish fish study in 1981.19,20 However, their global distribution is only now

becoming fully recognized.

Similar to PCBs and PBBs, BDEs are used commercially as mixtures, and 209

different congeners are theoretically possible, varying in their degree of halogena￾tion. Three major commercial products are produced: Deca-, Octa-, and Penta-BDE

(formulation designations will be capitalized to differentiate them from individual

congener designations). Global BDE demand for the total of all three mixtures