Michael L. Carson

Cancer risk for chemical workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Aims: To describe the long term mortality experience of a cohort of 2187 male chemical production workers previously exposed to substantial levels of dioxin. Methods: Vital status for a previously identified cohort was determined for an additional 10 years, to 1995. Dioxin exposures took place before 1983 and were sufficient to result in chloracne in 245 individuals. Mortality rates were compared with national figures and with a large pool of co-workers in unrelated production jobs. Results: All cancers combined (standardised mortality ratio (SMR) = 1.0, 95% CI 0.8 to 1.1) and lung cancer (SMR = 0.8, 95% CI 0.6 to 1.1) were at or below expected levels. Rates for soft tissue sarcoma (SMR = 2.4, 95% CI 0.3 to 8.6) and non-Hodgkin’s lymphoma (SMR = 1.4, 95% CI 0.6 to 2.7) were greater than expected overall, but below expectation in the update period. No trend of increasing risk with increasing exposure was observed for these cancers. Workers who developed chloracne had very low all-cancer rates (SMR = 0.5, 95% CI 0.3 to 1.0), and lung cancer rates (SMR = 0.3, 95% CI 0.0 to 1.1). Conclusions: We found no coherent evidence of increased cancer risk from dioxin exposure in this cohort. Our study highlights the wide range of cancer rates and the lack of consistency across dioxin studies.

Serum concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans among former Michigan trichlorophenol and pentachlorophenol workers

This study examines serum levels of 2,3,7,8-substituted chlorinated dioxins and furans, and PCBs for 375 Michigan workers with potential chlorophenol exposure, 37 Worker Referents, and 71 Community Referents. The chlorophenol workers were last exposed to trichlorophenol and/or pentachlorophenol 26–62 years ago. Employees working only in the trichlorophenol units had mean lipid-adjusted 2378-tetrachlorodibenzo-p-dioxin (TCDD) levels of 15.9 ppt compared with 6.5 ppt in the Worker Referents. Employees working only in the pentachlorophenol units had mean lipid-adjusted levels for 123478-H6CDD of 16.1 ppt, 123678-H6CDD of 150.6 ppt, 123789-H6CDD of 20.2 ppt, 1234678-H7CDD of 192.6 ppt, and OCDD of 2,594.0 ppt compared with the Worker Referent levels for the same congeners of 7.5, 74.7, 8.6, 68.7, and 509.1 ppt, respectively. All furan and PCB levels among workers in the trichlorophenol and/or pentachlorophenol departments were similar to the Worker Referents. The Tradesmen who worked throughout the plant had dioxin congener profiles consistent with both trichlorophenol and pentachlorophenol exposures. PCB levels and levels of 23478-P5CDF, 123478-H6CDF, and 123678-H6CDF were also greater in these Tradesmen than in the Worker Referents. The Worker Referent group had higher levels of dioxins and furans than the Community Referents indicating the potential for exposure outside the chlorophenol departments at the site. Distinct patterns of dioxin congeners were found many years after exposure among workers with different chlorophenol exposures. Furthermore, past trichlorophenol exposures were readily distinguishable from past pentachlorophenol exposures based on serum dioxin evaluations among workers. These data can be used to better assess dioxin exposures in future health studies.

Lipid-altering effects of different formulations of hydroxypropylmethylcellulose

BACKGROUND Hydroxypropylmethylcellulose (HPMC), a viscous, soluble dietary fiber, has been shown to be efficacious for lowering total and low-density lipoprotein cholesterol (LDL-C) concentrations. The relative effects of various dosages and viscosities of HPMC have not been fully evaluated. OBJECTIVE To examine the lipid-altering effects of several formulations of HPMC. METHODS In this randomized, double-blind pilot study, 165 men and women with primary hypercholesterolemia consumed a control product (snack bar or drink mix) or an HPMC-containing test bar or drink for 4 weeks. HPMC-containing products delivered 3, 5, or 10g of HPMC of low, moderate, moderately high, or high viscosity (9 HPMC groups, each with ∼15 subjects). RESULTS Data from drink and bar groups were combined because there was no evidence of a vehicle effect. The resulting analysis included data from the control and 6 HPMC dose and viscosity combinations. All HPMC groups showed LDL-C reductions ranging from 6.1 to 13.3% (P < .05 vs. baseline for 6 of the 7 groups), compared with a nonsignificant reduction (1.9%) in the control group. Changes in total and non-high-density lipoprotein cholesterol paralleled those for LDL-C. Concentrations of high-density lipoprotein cholesterol, triglycerides, apolipoprotein B, and high-sensitivity C-reactive protein were not significantly altered. CONCLUSION This pilot study provides preliminary evidence to support the efficacy of various formulations of HPMC for reducing cholesterol carried by atherogenic particles in men and women with primary hypercholesterolemia. Additional research will be required to more clearly define the roles of viscosity and dosage on the lipid-altering effects of HPMC.

Serum dioxin levels in former chlorophenol workers

Using gas chromatography/mass spectrometry, we measured lipid-adjusted serum levels for all 2,3,7,8-substituted dioxins and furans, and four coplanar polychlorinated biphenyls in 62 workers with chlorophenol exposure and 36 workers without chlorophenol exposures working at the same plant during the same time. We oversampled among workers diagnosed with chloracne. Mean dioxin background levels from 36 nonchlorophenol workers were estimated as 6.0 parts-per-trillion (ppt) for 2,3,7,8 tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and 67.5 ppt for 1,2,3,4,6,7,8 heptachlorodibenzo-p-dioxin (Hepta-CDD). We found different dioxin and furan profiles for trichlorophenol and pentachlorophenol (PCP) workers. Among trichlorophenol workers with chloracne, we found 2,3,7,8-TCDD (mean=30.5 ppt) above background levels and among PCP workers with chloracne, we found high levels of Hepta-CDD (mean=312.5 ppt) and other higher chlorinated dioxins and furans. Cumulative exposure estimates for dioxins for both 2,3,7,8-TCDD and the higher chlorinated dioxins created in the early 1980s for our epidemiology studies were highly correlated with serum dioxin levels when age and body mass index were taken into account. While workers previously diagnosed with chloracne had high serum dioxin levels, some workers without diagnosed chloracne also had high levels. Among tradesworkers with plant-wide responsibilities, we observed serum dioxins and PCB levels higher than background indicating workplace exposures. We estimate that the mean level of 2,3,7,8-TCDD present in the serum of workers on the date workplace exposure terminated was 267 ppt (ranging from 8 to 1184 ppt) assuming a 9-year half-life, 582 ppt (ranging from 10 to 2,641 ppt) assuming a 7-year half-life, and 1928 ppt (ranging from 22 to 17,847) when a toxicokinetic model is used. We conclude that our findings are consistent with other studies reporting high serum dioxin levels among chlorophenol workers after occupational exposures.

Chlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyl profiles of workers with trichlorophenol and pentachlorophenol exposures

We examined the serum lipid adjusted levels of 2,3,7,8-substituted chlorinated dioxins and furans, and four coplanar PCBs for 98 workers. We found workers who worked only in the trichlorophenol units had mean lipid adjusted 2,3,7,8-TCDD levels of 36.8 ppt significantly higher (p<0.05) than 6.0 ppt in the reference group. Workers who worked only in the pentachlorophenol units had mean lipid adjusted levels for 123478-HxCDD of 14.8 ppt, 123678-HxCDD of 156.4 ppt,123789-HxCDD of 23.7 ppt, 1234678-HpCDD of 234.6 ppt, and OCDD of 2,778.2 ppt significantly higher (p<0.05) than the reference group levels for the same congeners of 7.5, 71.8, 8.0, 67.5, and 483.2 ppt, respectively. While we did find 12378-PeCDD levels higher than the reference group in trichlorophenol and pentachlorophenol workers, the differences are small, and could be attributed to normal variation. All furan levels among the trichlorophenol or pentachlorophenol only workers were not significantly different than the reference group. Workers with both trichlorophenol and pentachlorophenol exposures had mean dioxin levels consistent with complex chlorophenol exposures. Tradesmen who worked throughout the plant had congener profiles consistent with both trichlorophenol and pentachlorophenol exposures. PCB 169, 23478-PeCDF, 123478-HxCDF, and 123678-HxCDF levels were also significantly greater (p<0.05) in these tradesmen than in the reference group. We found distinct patterns of dioxin congeners many years after exposure among workers with different chlorophenol exposures. We were effectively able to distinguish past trichlorophenol exposures from pentachlorophenol exposures based on differing serum dioxin profiles among workers.

Dose–Response Characteristics of High-Viscosity Hydroxypropylmethylcellulose in Subjects at Risk for the Development of Type 2 Diabetes Mellitus

BACKGROUND Hydroxypropylmethylcellulose (HPMC) is a modified cellulose fiber that creates a viscous solution in the gastrointestinal tract. The present study examined the dose-response characteristics of high-viscosity (HV)-HPMC consumption on postprandial glucose and insulin levels in men and women at increased risk for type 2 diabetes mellitus. METHODS Subjects were a subset of participants in two trials with elevated peak postprandial glucose [>or=7.8 mmol/L (>or=140 mg/dL)] and body mass index (BMI) >or=27 kg/m(2). Subjects (n = 39) consumed breakfast meals containing 75 g of carbohydrate, each of which contained 1, 2, 4, or 8 g of HV-HPMC or a cellulose control in a randomized, double-blind manner. Each subject completed tests with control and two HV-HPMC doses. RESULTS Peak glucose concentration was lower than control (all P < 0.01) following 2 g (10%), 4 g (18%), and 8 g (20%) of HV-HPMC. Peak insulin was also reduced (P < 0.01) following 2 g (32%), 4 g (35%), and 8 g (46%) of HV-HPMC doses versus control. Incremental areas for glucose from 0 to 120 min were reduced by 8-40% versus control but only reached significance for the 4-g and 8-g conditions, whereas incremental areas under the insulin curves were reduced by 14-53% (P < 0.01 for 2, 4, and 8 g of HV-HPMC). CONCLUSIONS Among subjects at risk for type 2 diabetes mellitus, 1.0-8.0 g of HV-HPMC blunted postprandial glucose and insulin responses in a dose-dependent manner. Additional research is warranted to assess whether chronic consumption might retard the development or progression of glucose intolerance.

Incidence of Occupational Asthma and Exposure to Toluene Diisocyanate in the United States Toluene Diisocyanate Production Industry

Objective: This study examines asthma risk in facilities producing toluene diisocyanate (TDI). Methods: A total of 197 workers were monitored from 2007 to 2012. TDI air concentrations were used to estimate exposures. Results: The incidence of cases consistent with TDI-induced asthma was 0.009 per person-years (seven cases) or consistent with TDI-induced asthma or asthma indeterminate regarding work-relatedness was 0.012 (nine cases). Increased risk of cases consistent with TDI asthma was observed for cumulative (odds ratio [OR] = 2.08, 95% confidence interval [CI] 1.07 to 4.05) per logarithm parts per billion-years and peak TDI exposures (OR = 1.18, 95% CI 1.06 to 1.32) (logarithm parts per billion). There was a weak association with cumulative and peak exposures for decline of short-term forced expiratory volume in one second (FEV1). Asthma symptoms were associated with workers noticing an odor of TDI (OR 6.02; 95% CI 1.36 to 26.68). Conclusions: There is evidence that cumulative and peak exposures are associated with TDI-induced asthma.

Results From the US Industry-Wide Phosgene Surveillance: The Diller Registry

Objective: In 2004, The American Chemistry Council Phosgene Panel established a phosgene exposure registry among US phosgene producers with the primary purpose of monitoring health outcome information for workers with acute exposure. Methods: We examine symptoms among 338 workers with phosgene exposure. The phosgene exposures averaged 8.3 ppm-minutes ranging up to 159 ppm-minutes with most exposures below 10 ppm-minutes. Results: We found that the level of phosgene exposure in ppm-minutes was related to workers reporting mostly irritation symptoms of the nose, throat and eyes within 48 hours of exposure. However, we found no relationship between phosgene exposure and the presence of symptoms 30 days after exposure. Conclusions: These findings lend credence to the theory that prolonged respiratory effects do not occur with doses less than 150 ppm-minutes.

Medical Monitoring for Occupational Asthma Among Toluene Diisocyanate Production Workers in the United States

Objective: The aim of this study was to describe a study of medical monitoring methods and lessons learned in detecting health outcomes in U.S. plants producing toluene diisocyanate (TDI). Methods: A multidisciplinary team implemented a medical and environmental monitoring program in three TDI plants. Results: Of 269 eligible workers, 197 (73%) participated and 42 (21%) met symptom and/or lung function criteria that would trigger evaluation for possible asthma over 5 years of data collection. Subsequent evaluation was delayed for most, and a web-based data collection system improved timeliness. Conclusion: Medical monitoring of TDI workers identified workers triggering further assessment per study protocol. Systems and/or personnel to ensure rapid follow-up are needed to highlight when triggering events represent potential cases of asthma needing further evaluation. Implementation of a research protocol requires resources and oversight beyond an occupational health program.

Longitudinal and Cross-sectional Analyses of Lung Function in Toluene Diisocyanate Production Workers

Objective: The aim of this study was to investigate lung function among toluene diisocyanate (TDI) production workers. Methods: One hundred ninety-seven U.S workers performed spirometry from 2006 through 2012. Results were compared within the study cohort and with U.S. population measures. A mixed-effects model assessed factors affecting repeated forced expiratory volume in 1 second (FEV1) measurements. Results: The cohorts mean FEV1 and forced vital capacity (FVC) percent reference values, although greater than 90%, were significantly lower and the prevalence of abnormal spirometry (predominantly restrictive pattern) was significantly higher than in the U.S. population. Differences in lung function among workers with higher cumulative TDI exposure were in the direction of an exposure effect, but not significant. Conclusion: We found little evidence of an adverse effect of TDI exposure on longitudinal spirometry in these workers. The association between TDI exposure and the increasing prevalence of a restrictive pattern needs further exploration.