Contamination of the food chain by polychlorinated biphenyls from a broken transformer

Environmental- and injury-related epidemic-assistance investigations, 1946-2005

This paper summarizes environmental investigations (n = 458) conducted during the first 60 years of the epidemic-assistance investigation program at the Centers for Disease Control and Prevention. These investigations were grouped into 10 categories: toxic chemicals (n = 102), indoor air quality and outdoor air toxics (n = 21), new or rare epidemic diseases and unexplained syndromes (n = 29), natural disasters (n = 81), terrorism and unintentional human-made disasters (n = 9), substance use and abuse (n = 13), environmental aspects of infectious disease (n = 132), those affecting neonates and infants (n = 11), violence and injuries (n = 51), and miscellaneous (n = 9). Among the most important or prominent were studies of lead and arsenic toxicity at smelters, mercury in paint and beauty creams, dioxin in waste oil in Missouri, polychlorinated biphenyls and multiple other toxic chemicals, global pesticide poisoning outbreaks, hepatic angiosarcoma among vinyl chloride workers, toxic oil syndrome in Spain, eosinophilia-myalgia syndrome from contaminated L-tryptophan, diethylene glycol poisoning in Haiti, aflatoxicosis in Kenya, Gulf War illness among veterans, impact and needs assessments during natural disasters (e.g., Hurricane Katrina (2005) and the Mount St. Helens volcano eruptions (1980)), risk factors for heat-related mortality, domestic and international terrorist attacks, Parkinsonism related to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in California, and unintentional injury- and violence-related events.

Background levels of polychlorinated biphenyls in the U.S. population

BACKGROUND

Polychlorinated biphenyl (PCB) exposures are encountered by the general public by eating contaminated food or living near a previously operating PCB factory or hazardous waste site. PCBs affect the immune, reproductive, nervous, and endocrine systems and are carcinogens. PCBs were banned in the United States in 1977. For public health, it is important to be able to estimate individual risk, especially for vulnerable populations, to monitor the decline in risk over time and to alert the public health community if spikes occur in PCB exposures, by measuring serum PCB levels. The historical decline in PCB exposures cannot be documented within a repeatedly tested general population, since there is no such population. Therefore, our aim was to model serum PCB levels in the US general population over time using published data.

METHODS

Models were developed based on 45 publications providing 16,914 background PCB levels in sera collected 1963-2003. Multiple linear regression and exponential decay were used to model the summary PCB levels.

RESULTS

Background levels of higher-chlorinated PCBs (five or more chlorines) in sera increased before 1979 and decreased after 1979; a quadratic model was the best fit. However, the exponential decay model explained better the low PCB serum levels still seen in the general population. For lower-chlorinated serum PCBs, no increase or decrease was shown (1.7ppb for all years).

CONCLUSIONS

Limitations for both models were lack of repeated measures, non-randomly selected study participants, selected years, concentration on geographic areas centered on PCB waste sites, lack of adjustment for BMI or for laboratory methods. Despite the limitations, this analysis shows that background PCB levels in the general population are still of concern. Future work should focus on uncertainties governing how to interpret the levels with respect to possible long term health effects.

Non-coplanar PCBs induce calcium mobilization in bottlenose dolphin and beluga whale, but not in mouse leukocytes

Polychlorinated biphenyls (PCBs) have been demonstrated to modulate marine mammal immune functions; however, the underlying mechanisms involved are poorly understood. Cytosolic calcium (Ca2+) is an important second messenger involved in numerous leukocyte functions. The direct effects of in vitro exposure to PCBs on Ca2+ mobilization were evaluated in leukocytes isolated from bottlenose dolphins, beluga whales, and B6C3F1 mice. Concentration- and time-response experiments with three non-coplanar PCBs (138, 153, 180), one coplanar PCB (169), and TCDD were tested. Exposure to the three non-coplanar PCBs significantly increased cytosolic Ca2+ in dolphin neutrophils, while PCB 180 significantly increased cytosolic Ca2+ in beluga neutrophils. Two non-coplanar PCBs (138 and 153) significantly increased Ca2+ in beluga monocytes, yet the response was delayed compared to that in neutrophils. Neither PCBs nor TCDD increased cytosolic Ca2+ in mouse neutrophils or monocytes. In experiments with Ca2+-free medium, only PCB 153 increased cytosolic Ca2+ in dolphin neutrophils, though the increase was less than that observed with Ca2+-supplemented medium, suggesting that extracellular Ca2+ was the predominant source for the rise in cytosolic Ca2+. Furthermore, in cells incubated with Ca2+-free medium, a significant increase in cytosolic Ca2+ was induced by thapsigargin following PCB exposure, indicating that intracellular Ca2+ was available, yet not mobilized by the PCBs, and further suggesting that PCBs mobilize extracellular Ca2+. These results demonstrate for the first time the direct effects of non-coplanar PCBs on Ca2+ mobilization in marine mammals, which may be involved in the modulation of phagocytosis previously observed in these species.

Modulation of the respiratory burst by organochlorine mixtures in marine mammals, humans, and mice

The effects of organochlorines (OC) on the immune systems of marine mammals and humans are poorly understood. One important innate immune function of peripheral blood neutrophils and monocytes is the respiratory burst, which generates reactive oxygen species (ROS) used to kill engulfed microorganisms. The present study characterized the immunomodulatory potential for mixtures of OCs, compared to that of individual OCs, on the respiratory burst in several marine mammals, humans, and B6C3F1 mice. The effects of three non-coplanar polychlorinated biphenyls (PCBs) (138, 153, 180), one coplanar PCB (169), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and all possible mixtures were tested upon in vitro exposure for 1 h, and their effects on the generation of a respiratory burst were measured by flow cytometry. The final concentration for each congener, alone or in a mixture, was 5 ppm for PCBs and 0.05 ppb for TCDD. Both significant enhancement and suppression of the respiratory burst occurred in all species tested, but the pattern was different between species and cell types (neutrophils vs. monocytes). Both coplanar and non-coplanar OCs were involved in the modulation of the respiratory burst. Regression analysis was not able to elucidate which OCs were involved in modulating the responses, highlighting the difficulty of developing models to predict the immunotoxic effects attributed to OC mixtures. The traditional mouse model and toxic equivalency (TEQ) approach both failed to consistently predict the toxicity of OCs in all species tested, questioning their applicability in the risk assessment process for all species. Elucidating the relative sensitivities to the immunomodulatory effects of OC mixtures between different species may have important implications for risk assessment as well as conservation and management strategies.

Patterns of PCBs and PCDD/PCDFs in chicken and pork fat following a Belgian food contamination incident

A food contamination incident involving polychlorobiphenyls (PCBs) and PCDD/Fs occurred in 1999 in Belgium. On heavily affected farms, concentrations of PCBs in chicken or pork fat exceeded the Belgium tolerance limit of 200 ng/g lipid weight for the sum of seven marker PCBs. Analysis of contaminated samples showed that the patterns for PCB and PCDD/F congeners differed among feed, chicken fat and pork fat. Lower chlorinated PCBs and polychlorodibenzofurans (PCDFs) including those with high TEFs (PCBs 105, 118, 126 and 2,3,4,7,8-PeCDF) were shown to either bioaccumulate more in chicken fat or to be eliminated more readily in pork. This leads to the possibility that consumption of chicken would result in a higher TEQ human body burden than that from the same consumption of pork. In addition, PCDF congeners with non-2,3,7,8-substitution (e.g., 1,2,4,7,8-PeCDF) were present in chicken fat but absent in pork fat. Since the residue pattern in this commercial episode changes less in the avian species, these results reinforce the value of birds rather than mammals as markers of the source of contamination with persistent organochlorine pollutants.

Human tissue monitoring and specimen banking: opportunities for exposure assessment, risk assessment, and epidemiologic research

A symposium on Human Tissue Monitoring and Specimen Banking: Opportunities for Exposure Assessment, Risk Assessment, and Epidemiologic Research was held from 30 March to 1 April 1993 in Research Triangle Park, North Carolina. There were 117 registered participants from 18 states and 5 foreign countries. The first 2 days featured 21 invited speakers from the U.S. Environmental Protection Agency, the Centers for Disease Control and Prevention, the National Institute of Environmental Health Sciences, various other government agencies, and universities in the United States, Canada, Germany, and Norway. The speakers provided a state-of-the-art overview of human exposure assessment techniques (especially applications of biological markers) and their relevance to human tissue specimen banking. Issues relevant to large-scale specimen banking were discussed, including program design, sample design, data collection, tissue collection, and ethical ramifications. The final group of presentations concerned practical experiences of major specimen banking and human tissue monitoring programs in the United States and Europe. The symposium addressed the utility and research opportunities afforded by specimen banking programs for future research needs in the areas of human exposure assessment, risk assessment, and environmental epidemiology. The third day of the symposium consisted of a small workshop convened to discuss and develop recommendations to the U.S. Environmental Protection Agency regarding applications and utility of large-scale specimen banking, biological monitoring, and biological markers for risk assessment activities.

Potential reproductive and postnatal morbidity from exposure to polychlorinated biphenyls: epidemiologic considerations

There is both laboratory and epidemiologic evidence that PCBs are toxic to several phases of reproduction. Workplace exposure is an important but small part of the exposure to these compounds, since most of the population has detectable levels in blood or fat. Studies in the general population on PCBs and reproduction have not been done. Some studies in workers are under way, and in epidemic PCB poisonings, small babies with a distinct clinical syndrome are seen. We review some of the laboratory and epidemiologic data and the methods available for study of reproduction in humans; study of any highly exposed group should be done and studies of spontaneous abortion, birth weight and certain congenital anomalies should look for an effect of PCBs.

Symptoms, signs and findings in humans exposed to PCBs and their derivatives

The records of the health effects caused by some accidental exposure and findings from medical examination in cases exposed to polybrominated biphenyls (PBB) as well as to polychlorinated biphenyls (PCB) and their derivatives polychlorinated dibenzofurans (PCDF) and dibenzodioxins (PCDD) have provided some information for the recognition and classification of their toxicity in humans. The most impressive clinical features have been presented by the yusho episode of exposure. Dermatologic signs are the most persistent indicator of a considerable uptake. Neurological symptoms, respiratory findings and impairment of liver function are further aspects of the contamination. Skin manifestations have been observed also in the newborn infants from mothers exposed to high levels of the substances. However, the available data make it still hard to assess the clinical picture of the effects on humans in cases of acute exposure and even more the effects on reproduction and long-term effects. Furthermore it would still be arbitrary to draw a line between the symptoms which can be referred to PCBs and PBBs alone and those which can be related qualitatively and quantitatively to PCB derivatives (PCDFs, PCDDs, PCQs).