Contaminant Exposure Profiles Demonstrate Similar Physiological Effects Across Environments Despite Unique Profile Composition in Formosa, Argentina, and Connecticut, USA

OBJECTIVE

Exposure to environmental contaminants is globally universal. However, communities vary in the specific combination of contaminants to which they are exposed, potentially contributing to variation in human health and creating "locally situated biologies." We investigated how environmental exposures differ across environments by comparing exposure profiles between two contexts that differ markedly across political, economic, and sociocultural factors-Namqom, Formosa, Argentina, and New Haven, Connecticut, United States.

METHODS

We collected infant urine, maternal urine, and human milk samples from mother-infant dyads in Formosa (n = 13) and New Haven (n = 21). We used untargeted liquid chromatography with high-resolution mass spectrometry (LC-HRMS) to annotate environmental contaminants and endogenous metabolites in these samples, and we analyzed the data using exposome-wide association studies (EWAS) followed by pathway enrichment.

RESULTS

We found statistically significant differences between the chemical exposure profiles of the Argentinian and US mothers, mostly involving pesticides; however, we observed similarities in the infant urine and human milk environmental contaminant profiles, suggesting that the maternal body may buffer infant exposure through human milk. We also found that infants and mothers were exposed to contaminants that were associated with alterations in amino acid and carbohydrate metabolism. Infants additionally showed alterations in vitamin metabolism, including vitamins B1, B3, and B6.

CONCLUSIONS

Differences in chemical exposure profiles may be related to structural factors. Despite variation in the composition of exposure profiles between the two study sites, environmental contaminant exposure was associated with similar patterns in human physiology when we considered contaminants comprehensively rather than individually, with implications for metabolic and cardiovascular disease risk as well as infant cognitive development.

The contribution of the Clinica del Lavoro of Milan to the development of industrial hygiene and toxicology in the twentieth century

In 1910, the founder of the Clinica del Lavoro of Milan, Luigi Devoto established a chemistry laboratory in the new institute, sustaining its importance in the study of occupational diseases. In 1948, the new director of the Clinica, Enrico C. Vigliani established the first laboratory of industrial hygiene in Italy, in the years of the economic boom. In 1960s, this laboratory, directed by Nicola Zurlo, significantly contributed to the research in the field. In 1980s and 1990s, the laboratory of the Clinica started to explore the field of environmental toxicology, studying the effects of benzene and other traffic pollutants on the general population. The analysis of history of the Clinica del Lavoro of Milan may represent a valuable tool for studying the origin and the development of industrial hygiene, occupational and environmental toxicology in the twentieth century.

Biomarker measurements in a coastal fish-eating population environmentally exposed to organochlorines

The Lower North Shore region of the St. Lawrence River is home to a fish-eating population that displays an unusually high body burden of several organochlorines, including polychlorinated biphenyls (PCBs) and dioxin-like compounds (DLCs). We measured biomarkers indicative of liver enzyme induction and investigated the relationship with organochlorine body burden in adult volunteers from this population. We determined plasma concentrations of PCBs and chlorinated pesticides by high-resolution gas chromatography (HRGC) with electron capture detection. DLC concentrations were measured by the dioxin-receptor chemically activated luciferase expression (DR-CALUX) assay and in a subset of participants, by HRGC/high-resolution mass spectrometry. We measured cotinine, d-glucaric acid, and porphyrins in morning urine samples and determined liver CYP1A2 activity in vivo using the caffeine breath test. Neither DLC concentrations as measured by the DR-CALUX nor PCB-153 concentrations, the latter representing total PCB exposure, were correlated with biomarkers of effects. Smoking (morning urinary cotinine concentration) was positively related to CYP1A2 activity as measured by the caffeine breath test (p < 0.01). Liver CYP1A2 activity was in turn negatively correlated with PCB-105:PCB-153 and PCB-118:PCB-153 congener ratios (p < 0.05). Hence, despite the relatively high body burden of PCBs and DLCs in this population, only smoking had a significant correlation with biomarkers of hepatic enzyme induction. Our data are consistent with smoking-induced liver CYP1A2 activity altering heme metabolism and increasing the biotransformation of mono-ortho PCB congeners.

Human Exposure to Polychlorinated Biphenyls and Health Effects

Polychlorinated biphenyls (PCBs) are a mixture of chemicals. Some congeners of the mixture are highly persistent both in the environment and in humans. Although PCBs have not been used commercially since about 1977 in the US, they can still be detected in human blood and tissues in this country. PCB levels are declining and are often no longer detectable in younger people. A cursory review of recent animal studies is provided. Studies to determine whether PCBs cause cancer in humans, neurobehavioural effects, abnormal thyroid and immune function in children and low birth weight are discussed in more detail. These studies are inconclusive and do not provide clinical evidence that PCBs at levels encountered with human exposure produce adverse health effects. The differences in PCB blood or tissue concentrations between controls and cases, or between the upper and lower end of various environmentally exposed groups of children or adults, are small. Although some effects are statistically significantly different, they do not appear to be biologically significant. Many studies on the effects of PCBs are difficult to interpret because the range of normal values for clinical and neurobehavioural tests are not provided or appropriately considered, there was no, or inadequate, control for potential confounders. In occupational mortality studies, exposures were much higher. In some studies, various specific cancers were elevated. However, these appear to be chance observations resulting from multiple comparisons since the increase of specific cancers was not consistent between studies and was no longer present in some cohorts when studies were repeated at a later date with longer follow-up. Overall, the data fail to demonstrate conclusive adverse health effects of PCBs at concentrations encountered with human exposures.

Polychlorinated biphenyls (PCBs) and human health: an update

Polychlorinated biphenyls (PCBs) are a mixture of 209 different chlorinated biphenyl congeners (forms) of which 36 are environmentally relevant. PCBs are lipid (fat)-soluble, stable compounds. PCBs may be contaminated with more highly toxic polychlorinated dibenzofurans (PCDFs). Some PCDFs were primarily responsible for the two poisoning outbreaks--Yusho and Yu-Cheng. Based on the reports on workers and the general population, no clear and convincing evidence that PCB exposures were casually associated with adverse health effects was advanced; this included cancer for a wide range of body burdens and exposures for serum PCB concentrations > 1000 ppb (micrograms/l) and adipose PCB levels > 400 ppm (mg/kg). No meaningful reproductive problems have been identified in female capacitor workers. In the opinion of the review author, the available evidence for cancer and for reproductive effects is inconclusive. Adverse neurobehavioral effects in infants and young children have been reported in a study of women in the general population and a study of fish eaters and their offspring. The adverse effects observed in the two studies were not the same; the exposure assessments in both studies are not well defined and have many uncertainties. Subhuman primates appear to be more sensitive to reproductive and other adverse effects of PCBs than humans. Obvious external clinical signs are observed in the offspring of subhuman primates at dosage levels below those experienced by female capacitor workers and members of the general population prior to the control of PCBs.

Studies of transformer repair workers exposed to PCBs: II. Results of clinical laboratory investigations

Thirty-eight transformer repairmen currently exposed to polychlorinated biphenyls (PCBs), 17 former transformer repairmen, and 56 comparison workers not known to be exposed to PCBs were studied. Measurements were made of serum liver function tests, gamma-glutamyl transpeptidase (GGT), lipid profile, thyroid function tests, and other serum biochemistry; hemoglobin; white cell count; 24-hour excretion of delta-aminolevulinic acid, porphyrins, 17-hydroxycorticosteriods and 17-ketosteroids; sperm count; spirometry; and antipyrine half-life to evaluate microsomal mixed function oxidase induction. The total exposed group differed significantly from the comparison group in albumin, LDH, T4, T4-RT3 index, and actual/predicted FEV1. Significant differences among all three exposure groups were seen for albumin, T4, T4-RT3 index, and 17-hydroxycorticosteroid excretion. Differences in FEV1 were attributable to smoking. Significant correlations between serum PCBs and serum lipids were removed by adjustment for confounding variables. After adjustment for confounding variables, there was a statistically significant positive correlation between serum PCBs and GGT and a negative correlation between adipose PCBs and 17-hydroxycorticosteroid excretion. These may reflect subtle metabolic effects of PCBs.

Urinary porphyrins in children exposed transplacentally to polyhalogenated aromatics in Taiwan

In 1979, there was a large (greater than 2,000 cases) outbreak of poisoning due to contaminated rice oil in central Taiwan. The causal agent was a mixture of thermally degraded polychlorinated biphenyls (PCBs), polychlorinated quaterphenyls, and polychlorinated dibenzofurans, which had become mixed with the oil during processing. Patients remained symptomatic for several years afterward, and the chemicals persisted in their tissue. Women who became pregnant had children with high perinatal mortality and a dysmorphic syndrome. We examined urines from 75 children born to exposed mothers after the oil was confiscated, 74 controls, and 12 sibs of the exposed children. Four of the transplacentally exposed children, 2 controls, and 1 sib had a type B hepatic porphyria (i.e., uroporphyrin greater than coproporphyrin); total porphyrin excretion was elevated in the exposed children as a group (95 vs. 81 micrograms/L); and 8 of the 75 exposed children and 2 controls had total urinary porphyrin concentrations of greater than 200 micrograms/L.

Porphyrinurias and occupational disease

Pathologic porphyrinuria in man is based on a complex etiology and pathogenesis. In hepatic porphyrias, coproporphyrinuria is usually only one of the pathognomostic porphyrin parameters in the urine. Secondary coproporphyrinuria means that an increased excretion of coproporphyrin occurs as the biochemically dominant symptom of a disturbance in porphyrin and heme metabolism during an intoxication, individual condition, or basic disease. Certain foreign and environmental chemicals, such as hexachlorobenzene, polyhalogenated aromatic hydrocarbons, vinyl chloride, and dioxin, alter the heme pathway functionally. Increased porphyrinuria can follow as a toxic response that is differentiated into secondary coproporphyrinuria and chronic hepatic porphyria. This is characterized by a simultaneous increase in hepatic and urinary uroporphyrin and heptacarboxylic porphyrins, owing to inhibition of hepatic uroporphyrinogen decarboxylase. Most of the coproporphyrinurias observed in man are caused by alcohol ingestion. Dioxin, vinyl chloride, and polyhalogenated biphenyls induce an incipient subclinical stage of chronic hepatic porphyria in persons with normal red cell uroporphyrinogen decarboxylase. In contrast, exposure to dioxin on the part of persons with inherited uroporphyrinogen decarboxylase deficiency can cause latent chronic hepatic porphyria to develop into PCT. Coproporphyrinuria and latent chronic hepatic porphyria do not produce clinical symptoms. Secondary porphyrinuria with transition to chronic hepatic porphyria is a metabolic response following various toxic and pathologic conditions; it serves as a sensitive index for chemical exposure and occupational disease.

Pilot survey of urinary porphyrins from persons transiently exposed to a PCB transformer fire

In rats and humans chronically exposed to large amounts of PCB (polychlorinated biphenyls) and PCDF (polychlorinated dibenzofurans), the urinary excretion of uroporphyrin and coproporphyrin are altered. However, porphyrin excretion in humans after acute transient low level exposure has not been evaluated. Following such an exposure in which bystanders and firefighters were in contact with smoke from a PCB transformer fire, we surveyed 90 self-referred individuals by questionnaire and by determining single 24 hour urinary excretion of uroporphyrin and coproporphyrin 2-4 weeks after the fire. Questionnaire variables that assessed exposure were not associated with the magnitude of either uroporphyrin or coproporphyrin excretion. Uroporphyrin excretion was slightly elevated in nine subjects (range 66-106 micrograms/24 hours, normal less than 60), which is much less than in clinical cases of porphyria cutanea tarda. Uroporphyrin excretion was inversely correlated with coproporphyrin excretion (r = -0.3844, p = 0.0002). For 5 subjects (3 with elevated initial uroporphyrin excretion) retested at 3-4 weeks after the fire, all 5 showed increases in uroporphyrin and decreases in coproporphyrin excretion when compared to initial determinations. These two reciprocal relationships would be the expected result from inhibition of uroporphyrinogen decarboxylase, a known experimental effect of PCB and PCDF in mice. Overall, urinary porphyrin excretions were not altered or sensitive measures of exposure.

Liquid chromatography of urinary porphyrins for the biological monitoring of occupational exposure to porphyrinogenic substances

Very sensitive and precise analytical methods for measuring total porphyrin excretion and the relative amounts of different porphyrins in urine are required in order to monitor the biological effects of porphyrinogenic substances in workers and the general population. Many analytical steps of a HPLC method for measuring porphyrins as methyl esters in urine have been perfected. Sensitivity is 0.1 microgram/1 for each type of porphyrin, and average recovery is 92% in the range of 50-450 micrograms/liter porphyrins. The coefficient of variation is 3.4% within a series and 12.5% between series. Chemical oxidation before analysis and appropriate storing of the samples are the key points in achieving high quality results. The urinary excretion of porphyrins in healthy male workers varies within the range 21 to 161 micrograms/liter (95% limits of a group of 78 subjects). Concomitant factors, like drug use or liver disorders, were found to alter urinary porphyrin excretion. The proposed method permits the detection of extremely small alterations in porphyrin excretion resulting from occupational exposure to industrial chemicals such as, for example, mild coproporphyrinuria or early stages of chemical porphyria induced by polyhalogenated arylhydrocarbons.