Particles suspended in the water column are affected by hydrodynamic conditions. PCBs that are freely dissolved or associated with DOC can cross the sediment-water interface and move between the deeper sediments below the bioturbation or bioactive surface sediment and the surface sediment.
This movement is largely a function of diffusion between the sediment pore water, and the overlying water column. It is dependent on the detailed hydrodynamic structure at the water-sediment interface and can be greatly enhanced by bioturbation caused by organisms living in the sediments.
Freely dissolved PCBs in the water column are also subject to volatilization across the air-water interface. Such loss can be substantial, especially in systems that provide substantial time for the water-air interactions. Transformations of PCBs can also occur in aquatic systems by microbial degradation in aerobic water columns and surficial sediments , reductive dechlorination in anaerobic sediments , and metabolism via organisms that. DOC can include colloidal materials that are mostly organic matter.
Metabolism by microorganisms Mavoungou et al. Because the susceptibility of PCBs to degradation and bioaccumulation is congener specific, the composition of PCB congener mixtures that occur in the environment differs substantially from that of the original industrial mixtures released into the environment Zell and Ballschmiter ; Giesy and Kannan ; Newman et al. In addition to environmental transformation products of PCBs, other chemicals, such as polyaromatic hydrocarbons PAHs , polychlorinated dibenzofurans PCDFs , polychlorinated dibenzo- p -dioxins PCDDs , pesticides, and metals, might be present in contaminated sediments.
Generally, the less-chlorinated congeners are more water soluble, more volatile, and more likely to biodegrade. Therefore, lower concentrations of these congeners are found in sediments compared with the original concentrations of Aroclors that entered the environment. Higher-chlorinated PCBs are often more resistant to degradation and volatilization and sorb more strongly to particulate matter.
Some of these more-chlorinated PCBs tend to bioaccumulate to greater concentrations in tissues of animals than do lower-molecular-weight PCBs. The more-chlorinated PCBs can also biomagnify in food webs see Box , and other higher-molecular-weight congeners have specific structures that make them susceptible to metabolism by enzymes once these congeners are taken up by such species as fish, crustacea, birds, and mammals.
The low vapor pressure of PCBs, coupled with air, water, and sediment transport processes, means that they are readily transported from local or regional sites of contamination to remote areas Risebrough et al. PCBs can enter a global biogeochemical cycle that transports them far from their initial source of input. This global biogeochemical cycling of PCBs is the result of volatilization losses from tropical and subtropical waters to the atmosphere.
These atmospheric PCBs move from warmer regions to polar regions, especially in the northern hemisphere, where they are deposited to soil and water surfaces Muir et al. Table 2—2 presents some atmospheric concentrations of PCBs from various regions of the world, illustrating the scale and variability of their global distribution. Humans and wildlife can be exposed to PCBs either directly from contact with contaminated air, sediments, or water or indirectly through the diet.
Bioaccumulation —The net accumulation of PCBs by an organism as a result of uptake from all routes of exposure i. Food Web Transfer —The movement of PCBs in the tissue of prey to the tissue of the predator, repeated one or more times in the food web, where the predator of the first transfer is the prey in the next step Van Leeuwen and Hermens Biomagnification —The tendency of PCBs to accumulate to higher concentrations at higher levels in the food web through dietary accumulation Suter Bioavailability —The ratio of the amount of PCBs taken into the organism and thus available to internal tissues, compared to the amount of PCBs ingested into the gut, inhaled into the lungs, or in direct contact with the skin Suter When considering exposure pathways, it is imperative to assess the biologically available fraction of PCBs.
In sediments, PCBs can be buried below the biologically active zone and, therefore, are less available for uptake by aquatic organisms. The biologically active zone is the top layer of sediments, typically 5—10 centimeters cm deep. This layer is continuously reworked by sediment-dwelling organisms and remains in contact with the overlying water. PCBs that are strongly sorbed to organic sediment particles in the biologically active zone tend to have reduced bioavailability to organisms that ingest or are exposed to these sediments EPA Consumption of PCB-contaminated foods is the most significant route of exposure to PCBs for the general human population Newhook ; Birmingham et al.
This exposure occurs as a result of bioaccumulation of PCBs through the food chain. For example, PCBs can enter the aquatic food web via uptake by benthic invertebrates that are in close contact with the contaminated sediments. These invertebrates are eaten by other aquatic organisms, such as fish, and thus the PCBs migrate up the food.
Fish can accumulate PCBs by direct absorption through the gills and by eating contaminated sediments, insects, and smaller fish. Evans et al. Studies have shown that there is a significant correlation between the amount of fish consumed and the organochlorine body burden in humans Fitzgerald et al.
Some populations, such as the Inuits of northern Canada, whose diet consists largely of fish and marine mammals e. Although dermal contact and absorption through the skin are possible exposure routes for PCBs, such exposures are typically limited to the occupa-.
At some sites, however, such as along parts of the Housatonic River in Massachusetts, PCB concentrations in riverbank surfaces and sediments represent a potential route of exposure for populations in the vicinity. At these sites, PCB concentrations have been high enough to warrant concerns and public-health warnings against any dermal contact with the sediments NRC b.
The biological activity of PCBs is congener specific, and, therefore, different mixtures of PCBs will have different biological and toxicological activity. The potency with which individual PCB congeners bind to the AhR is correlated with their ability to elicit dioxin-like effects. These factors provide a means of pooling and comparing different mixtures of PCB congeners.
One of the main endpoints on which TEFs are based is the induction of CYP1A1 sometimes described as induction of arylhydrocarbon hydroxylase or microsomal cytochrome P enzymes, or 3-methylcholanthrene-like induction.
This process involves binding of the dioxin-like PCB molecule with the AhR in cytosol, association of the bound complex with a nuclear translocation factor, translocation of this ternary complex to the nucleus, and binding of the complex to a specific DNA sequence, the dioxin-responsive element DRE. This endpoint, however, is not necessarily an adverse health effect. The congeners that exhibit the highest TEF values tend to be the planar, most highly substituted forms, with lateral chlorine substitution.
Noncoplanar congeners and congeners with low levels of chlorination are rated at very low TEF values; yet they have been associated with immunological and neurobehavioral endpoints see review by Fischer et al. The toxicity of the. Therefore, although TEFs are useful in PCB risk assessments, they should not be relied on without considering other risks.
In addition to the effects of planar PCBs, studies have shown that noncoplanar PCBs elicit neurotoxic effects in exposed animals and in cell cultures Kodavanti et al. Recently, experiments have been conducted to investigate the mechanism or mechanisms that underlie the neurotoxic effects of the noncoplanar PCBs; some of those effects are not mediated by the Ah receptor Kodavanti and Tilson but rather by the signal transduction pathways.
PCBs have been shown to affect tyrosine kinase, protein kinase C, and phospholipase A2. Intracellular calcium homeostasis is also affected by noncoplanar PCBs see reviews by Kodavanti and Tilson ; Tilson et al. Some PCB congeners also appear to have estrogenic and antiestrogenic effects, possibly mediated by interactions with one or more steroid receptors. PCBs affect the metabolism of thyroid hormones through the induction of enzymes involved in thyroid hormone metabolism.
PCBs also affect the immune system. Effects on the immune system seem to occur through both AhR- and non-AhR-mediated mechanisms. PCBs might also increase oxidative stress, which might contribute directly to carcinogenesis Amaro et al. This mechanism would explain PCB-induced cancer with no direct involvement of any receptor and is consistent with observations that PCBs are generally negative in conventional mutagenicity bioassays and have not been shown to form DNA adducts.
PCBs can be metabolized and that metabolism can affect their toxicity, sometimes increasing toxic potential. For example, hydroxylated PCBs that interact with the estrogen receptor and exert estrogenic or antiestrogenic effects can be formed Connor et al. The Yusho incident occurred in Japan in and involved more than 1, individuals ingesting rice oil contaminated with PCBs. Reported health effects of those exposed included acneform dermatitis, hyperpigmentation of the skin, aches and pain, peripheral nerve damage, and severe headaches.
The children born to affected mothers showed similar effects, in addition to decreased birth weight and impaired intellectual devel-. Studies of the human health ramifications of this incident continue and studies of the incident have been documented in numerous reports Kimbrough ; Erickson ; Safe A similar incident occurred in in Taiwan, where about 2, people consumed rice oil contaminated with PCBs Erikson However, in both the Yusho and Yucheng incidents, exposures to not only PCBs but also polychlorinated dibenzofurans, terphenyls, and quater-phenyls were considered to play an important role in the observed toxicity Erikson Most of the data on human health effects from exposures to PCBs are based on occupational exposures or consumption of contaminated fish.
Studies reported that increased serum PCB levels were statistically associated with neurobehavioral and developmental deficits in children exposed in utero and disruption of reproductive function and systemic health effects in adults self-reported liver disease and diabetes and effects on thyroid and immune system function. The NRC a reported evidence that human prenatal exposure to PCBs was associated with lower birth weight and shorter gestation Fein et al.
These studies were unable to determine whether any of the outcomes were the result of hormonal disruption by PCBs. In addition, epidemiological studies ATSDR of workers involved in the production and use of PCBs have reported increased mortality from cancer, although results have not been consistent across studies.
Data indicate that workers in capacitor manufacturing have increased incidences of liver, gallbladder, and biliary-tract cancer. Increased incidences of other specific cancers reported in exposed humans include gastrointestinal tract, malignant melanoma, lung, and brain cancers Cogliano These epidemiological studies are complicated by several factors that make interpretation of the results difficult.
These factors include exposure to. This concern regarding potential confounding factors was expressed recently in the report Toxicological Effects of Methylmercury NRC The effects of prenatal PCB exposures are similar to those of methylmercury.
The study population on which the NRC health recommendations for methylmercury were based also might have been affected by exposure to PCBs; therefore, exposures to PCBs had to be considered in the analysis of the data. Due to the limitations of the available human data, animal data are used to assess the potential for health effects following PCB exposures see Appendix G , Table G-1 , for a summary of mammalian toxicity doses and endpoints.
Animal studies have typically used commercial Aroclor mixtures for testing. However, as noted previously, these commercial mixtures differ substantially from the composition of PCBs typically found in sediments and from those to which humans are exposed through the consumption of contaminated fish and other foods.
Thus, the toxicity characteristics of the Aroclors and sediment PCB mixtures are different, as are the possible interactions between the various congeners. In studies on mature animals, the most sensitive observed effect is induction of microsomal P enzymes and liver enlargement for non-ortho-substituted and mono-ortho-substituted PCBs. However, in several developing animal species across vertebrate classes birds, mammals , functional or structural effects on the nervous system appear to be at least as sensitive to dioxin-like PCBs as is induction of the P enzymes Peterson et al.
PCB exposure in animals has also been associated with a wasting syndrome, reduced body weight, immunotoxicity, vitamin A deficiency, and thyroid deficiency; reproductive effects in offspring include reduced birth weight, abnormal gonad development, slowed learning and memory loss, and other behavioral changes Linet and Henshel ; Schantz et al. Following ingestion of diets containing Aroclor , benign liver tumors were observed in male mice. Kanechlor ingestion was associated with an increased incidence of hepatocellular carcinomas in male mice.
Ingestion of Aroclor induced liver tumors in rats of both sexes and hepatocellular carcinomas and liver adenocarcinomas in female rats. In a more recent study Brunner et al. Aroclor induced adenocarcinomas in the glandular stomach when fed to Fischer rats.
The consistent finding in these studies is the production of liver tumors that were benign in the majority of cases. The mechanism or mechanisms by which PCBs induce tumors in rodents remain unresolved. PCB mutagenicity studies, both in the presence and absence of a metabolic activation system, have generally been negative in bacterial, in vitro, and in vivo test systems. Therefore, PCBs and their metabolites do not appear to be mutagenic.
It is possible that the induction of cellular enzymes, including cytochrome Ps, could play a role in the carcinogenicity of PCBs, but exactly how that induction would lead to cancer has not been established. Although there is an overlap between the congeners present in sediments and those fed to rodents in the bioassay studies, there have been no animal studies conducted with congener mixtures actually found in sediments. Because the mixture of congeners present in sediment are site-specific, however, tests on individual congeners might be important to conduct so that the toxicity of a particular mixture could be extrapolated based on the toxicity of its component congeners.
The number of toxicity tests required to do so might be reduced by the careful use of structure-activity relationships. PCBs, especially di-ortho-substituted congeners, can also inhibit cellular gap junction intracellular communication, thus promoting tumor growth. ARNT is required by a number of other signal transduction pathways. Depletion of ARNT results in a wide range of pleiotropic effects. Laboratory and field studies with wildlife have demonstrated a causal link between adverse health effects and PCB exposure Giesy et al.
Chronic toxicity has been observed in fish, birds, and mammals; impacts include developmental effects, reproductive failure, liver damage, cancer,. There was also some evidence that PCBs can affect the immune system of birds Grasman et al.
Ecological exposure to PCBs is primarily an issue of bioaccumulation resulting in chronic effects rather than direct toxicity. PCBs bioaccumulate in biota by both bioconcentrating being absorbed from water and accumulated in tissue to concentrations greater than those found in surrounding water and biomagnifying increasing in tissue concentrations as they go up the food chain through two or more trophic levels.
At most contaminated sites, PCBs are predominantly bound to particles or strongly associated with an organic fraction. Therefore aquatic organisms are exposed to a combination of dissolved, sediment-associated, and food-associated PCBs. However, in terrestrial ecosystems, lower trophic level organisms are exposed to PCBs primarily through ingestion of soil and prey, although dermal absorption and inhalation might be important routes of exposure for certain species.
At each higher trophic level, certain PCB congeners are selectively enriched or depleted because of selective metabolism and excretion of metabolites. As a result, organisms at the top of the food chain are generally at the greatest risk of adverse effects due to exposure to PCBs. However, foraging preferences, species sensitivity, and other site-specific factors can modify the magnitude of those risks.
Long-term studies of the effects of PCBs on aquatic ecosystems have not been conducted. The report Hormonally Active Agents in the Environment NRC a , recommends that population studies be conducted to assess the impacts of PCBs on alterations of population size, age structure, and dynamics.
At present, many reports on the adverse effects of PCB exposures to wildlife are postmortem studies of individual animals turtles and birds found dead with high concentrations of PCBs in their bodies. Studies on a few specific populations of wildlife, such as mink, suggest that environmental contaminants including PCBs might be having a negative impact on the health of feral organisms. For example, Osowski et al. Examination of liver tissues of mink indicated that concentrations of PCBs 0.
A significant correlation was observed between PCB body burdens in wild mink and in fish collected from their home ranges in New York, indicating that the food chain is being affected Foley et al. Studies of some bird species in the Great Lakes region show evidence of population decline, reproductive impairment, or both in several fish-eating.
Many of the declines might be caused by eating contaminated fish. Although declines were initially likely to be caused by DDE-induced toxicity, the populations still exhibit subtle effects, such as deformities that might be caused by dioxin-like PCBs Giesy et al. It has been proposed that PCB concentrations in tree swallows nesting along the Hudson River might be responsible for their reduced reproductive success Secord and McCarty ; Secord et al.
In some locations, for example, the Niagara River, when wildlife health criteria values have been calculated and compared with the concentrations of PCBs found in local fish species, the amounts of PCBs in the fish have exceeded the criteria values Newell et al.
The ecological impacts of PCBs on wildlife have also been assessed in the laboratory. Most of the laboratory studies on wildlife have confirmed the field work.
However, these studies are problematic as controlled laboratory conditions cannot be used directly to predict effects in real-world populations because of changes in the concentrations and composition of PCBs as a function of space and time. Thus, the PCB mixture to which organisms are exposed at one time or at one location might be very different from that to which they are exposed in the laboratory or at other times or locations in the field.
The pattern of relative proportions of PCBs in environmental mixtures is variable and does not resemble the composition of the original technical PCB mixtures that were released into the environment Kannan et al. Furthermore, the relative concentrations of various PCB congeners differ according to trophic level and species. The compositions of PCB congener mixtures that occur in the environment differ substantially from those of the original technical Aroclor mixtures released to the environment Zell and Ballschmiter ; Giesy and Kannan ; Newman et al.
Weathering is a result of the combined effects of such processes as differential volatilization, solubility, sorption, anaerobic dechlorination, and metabolism, and results in changes in the composition of the PCB mixture over time and between trophic levels Froese et al.
Less-chlorinated PCBs are often lost rapidly due. Bioaccumulation in the tissues of animals is greater for more-chlorinated PCBs than for less-chlorinated PCBs; therefore, more-chlorinated PCBs are more likely to biomagnify in food webs.
Microbial reductive dechlorination of PCBs is a process shown to occur in a variety of anaerobic environments Bedard and Quensen This process does not remove all the chlorines and does not alter the basic structure of the biphenyl. The process results in a decrease in the concentrations of some congeners and an increase in others; therefore, the change in the total molar concentration of PCBs in sediments is generally not great. Reductive dechlorination occurs preferentially for chlorines in the meta and para positions, thereby selectively reducing the relative proportions of the PCBs that are laterally substituted.
These congeners are also those that tend to have the greatest potency to cause AhR-mediated effects. The absolute and relative concentration of this congener was reported to decrease by as much as to fold due to reductive dechlorination Quensen et al.
Furthermore, the bioavailability of the AhR-active congeners has been shown to be less than that for the di-ortho-substituted congeners. Thus, both processes, reductive dechlorination and selective sorption of coplanar PCB congeners, tend to reduce the toxicity of the mixture, relative to technical Aroclor mixtures, during the weathering process.
As was discussed above, the most accurate method of estimating the relative toxic potency of PCB mixtures is to measure the concentrations of individual congeners in tissues of receptors and correct their toxic potency by use of toxic potency factors.
It is not appropriate to use thermodynamic models to predict the movement of total PCB or TEQ concentrations from one matrix or trophic level to another. The movement of individual congeners, or at least those with more similar partitioning characteristics, should be modeled and the congeners should be corrected for their toxic potency. Thus, to model. When the toxicity of an example set of congener-specific concentrations in fish tissues to mink was estimated, it was found that the critical toxicant was the TEQ Foley et al.
PCBs are complex mixtures of chemicals that can have adverse effects on humans and wildlife. Therefore, the committee considers the presence of PCBs in sediments to pose potential long-term public health and ecosystem risks. It must be understood by all affected parties that even if the risks at a site are managed such that a specific sediment concentration of PCBs is achieved, over time PCB concentrations will slowly change due to numerous factors including atmospheric inputs from other sources and biodegradation.
Although considerable new information has become available in the past 2 decades and new information from field and laboratory studies is reported regularly, the committee finds that further research is particularly warranted in the following areas:. To collect such data, further elucidation of the various mechanisms of toxic actions will be required.
A better understanding of the contribution of PCB-contaminated sediments to the total global burden of PCBs is needed. Amaro, A. Oakley, U. Bauer, H. Spielmann, and L. Metabolic activation of PCBs to quinones: reactivity toward nitrogen and sulfur nucleophiles and influence of superoxide dismutase. Atlas, E. Global transport of organic pollutants. Ambient concentrations in remote marine atmosphere.
Science — Toxicological Profile for Polychlorinated Biphenyls Update. Environmental Protection Agency. In recent decades, regulators, academia, and industry have all paid increasing attention to the crucial task of determining how xenobiotic exposures affect biota populations, communities, or entire ecosystems.
For decades, PCBs have been recognized as important and potentially harmful environmental contaminants. The intrinsic properties of PCBs, such as high environmental persistence, resistance to metabolism in organisms, and tendency to accumulate in lipids have contributed to their ubiquity in environmental media and have induced concern for their toxic effects after prolonged exposure.
PCBs are bioaccumulated mainly by aquatic and terrestrial organisms and thus enter the food web. Humans and wildlife that consume contaminated organisms can also accumulate PCBs in their tissues.
Such accumulation is of concern, because it may lead to body burdens of PCBs that could have adverse health effects in humans and wildlife. PCBs are a probable human carcinogen. Studies of PCBs in humans have found increased rates of melanomas, liver cancer, gall bladder cancer, biliary tract cancer, gastrointestinal tract cancer, and brain cancer, [1] and may be linked to breast cancer. PCBs are known to cause a variety of types of cancer in rats, mice, and other study animals.
Instead, studies are undertaken of groups who have been exposed to a chemical, and if they suffer from more cancers than would be expected at normal levels, this may indicate that the chemical was a carcinogen.
However, there are many difficulties doing these studies: small numbers of people known to be exposed to a chemical; the fact that people suffer from many cancers without any chemical exposure; the fact that in some cases these people were exposed to a number of other chemicals; and the need to demonstrate high cancer rates that cannot be random in order to draw conclusions.
Acute toxic effects. People exposed directly to high levels of PCBs, either via the skin, by consumption, or in the air, have experienced irritation of the nose and lungs, skin irritations such as severe acne chloracne and rashes, and eye problems. Women exposed to PCBs before or during pregnancy can give birth to children with significant neurological and motor control problems, including lowered IQ and poor short-term memory.
A group of children in Michigan whose mothers had been exposed to PCBs were found to have decreased birth weight and head size, lowered performance on standardized memory, psychomotor and behavioral tests, and lowered IQ.
These effects lasted through at least 7 years. Women who consumed PCB-contaminated fish from Lake Ontario were found to have shortened menstrual cycles.
More highly-chlorinated PCBs with more chlorine atoms act like dioxins in altering the metabolism of sex steroids in the body, changing the normal levels of estrogens and testosterone. Immune system and thyroid effects. The animal studies were not able to identify a level of PCB exposure that did not cause effects on the immune system.
In humans, a recent study found that individuals infected with Epstein-Barr virus had a greater association of increased exposures to PCBs. It also increased the risk of non-Hodgkins lymphoma more than for those who had no Epstein-Barr infection.
This finding is consistent with increases in infection with Epstein Barr virus in animals exposed to PCBs. Since PCBs suppress the immune system and immune system suppression has been demonstrated as a risk factor for non-Hodgkin's lymphoma, suppression of the immune system is a possible mechanism for PCB-induced cancer. Immune effects were also noted in humans who experienced exposure to rice oil contaminated with PCBs, dibenzofurans and dioxins.
Taken together, the studies in animals and humans suggest that PCBs may have serious potential effects on the immune systems of exposed individuals. Reproductive effects of PCBs have been studied in a variety of animal species, including Rhesus monkeys, rats, mice and mink.
Rhesus monkeys are generally regarded as the best laboratory species for predicting adverse reproductive effects in humans.
Potentially serious effects on the reproductive system were seen in monkeys and a number of other animal species following exposures to PCB mixtures. Most significantly, PCB exposures were found to reduce the birth weight, conception rates and live birth rates of monkeys and other species; and PCB exposure reduced sperm counts in rats. Effects in monkeys were long lasting and were observed long after the dosing with PCBs occurred. Studies of reproductive effects have also been carried out in human populations exposed to PCBs.
Children born to women who worked with PCBs in factories showed decreased birth weight and a significant decrease in gestational age with increasing exposures to PCBs. Studies in fishing populations believed to have high exposures to PCBs also suggest similar decreases. This same effect was seen in multiple species of animals exposed to PCBs, and suggests that reproductive effects may be important in humans following exposures to PCBs.
Proper development of the nervous system is critical for early learning and can have potentially significant implications for the health of individuals throughout their lives. Effects of PCBs on nervous system development have been studied in monkeys and a variety of other animal species.
Newborn monkeys exposed to PCBs showed persistent and significant deficits in neurological development, including visual recognition, short-term memory and learning. Some of these studies were conducted using the types of PCBs most commonly found in human breast milk. Studies in humans have suggested effects similar to those observed in monkeys exposed to PCBs, including learning deficits and changes in activity associated with exposures to PCBs.
The similarity in effects observed in humans and animals provide additional support for the potential neurobehavioral effects of PCBs. There has been significant discussion and research on the effects of environmental contaminants on the endocrine system "endocrine disruption".
While the significance of endocrine disruption as a widespread issue in humans and animals is a subject of ongoing study, PCBs have been demonstrated to exert effects on thyroid hormone levels in animals and humans.
Thyroid hormone levels are critical for normal growth and development, and alterations in thyroid hormone levels may have significant implications. It has been shown that PCBs decrease thyroid hormone levels in rodents. Research has also shown that these decreases result in developmental deficits in rodents, including deficits in hearing.
PCB exposures have been associated with changes in thyroid hormone levels in infants in studies conducted in the Netherlands and Japan. Additional research will be required to determine the significance of these effects in the human population. Each IRIS assessment can cover a chemical, a group of related chemicals, or a complex mixture. Some substances are generally excluded from TSCA, including but not limited to, food, drugs, cosmetics and pesticides.
TSCA addresses the production, importation, use and disposal of specific chemicals including polychlorinated biphenyls PCBs , asbestos, radon and lead-based paint. The Federal Register Notices listed below include PCB-related rules proposed and final , notices of public meetings, responses to official comments, etc. This is not a comprehensive list of current regulations.
Petition for Exemption. However, it is possible that PCBs may be incidental contaminants in listed hazardous waste e. In these cases, wastes that otherwise meet a listing criteria or are characteristically hazardous are still subject to RCRA regulation regardless of PCB content. Section States may also have a regulatory program which is more stringent or broader in scope than the Federal program.
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