An epidemiologic investigation of forced expiratory volume at 1 second and respiratory symptoms among employees of a toluene diisocyanate production plant

The relationship between toluene diisocyanate exposure and respiratory health problems: A meta-analysis of epidemiological studies

Human epidemiological studies have shown inconclusive results over the effects of diisocyanates on respiratory health problems. A meta-analysis combined evidence on the association between occupational asthma (OA), respiratory function, and toluene diisocyanate (TDI) inhalation exposure. Sixty-one articles on occupational toluene diisocyanate exposure were identified via two databases. Fourteen studies were included in the meta-analysis. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the studies. Odds ratios (OR_asthma) for the association between TDI exposure compared to non-exposure and OA were calculated. The difference in mean differences (MD) of forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC), and the annual mean change differences-in milliliters per year (mL/yr)-in FEV₁ and FVC pulmonary function between TDI exposed and non-exposed, were calculated. When applicable, a random effects meta-analysis was performed. The overall summary OR_asthma for TDI exposed versus non-exposed was 1.18 (95% CI = 0.78-1.79). The summary of the predicted mean percentage difference (MD_%predicted) between exposed versus non-exposed was 2.96% for FEV₁ and 3.75% for FVC. A very small decrease of 5 mL/yr for FEV₁ and 10 mL/yr for FVC, respectively, was observed between the exposed and the non-exposed groups. There was moderate to low heterogeneity between study results, and most studies were evaluated as high-quality. This meta-analysis found no statistically significant adverse association between TDI occupational exposure and OA. No meaningful differences in lung function were detected between exposed and unexposed groups.

Critique of the ACGIH 2016 derivation of toluene diisocyanate Threshold Limit Values

In 2016, the American Conference of Governmental Industrial Hygienists (ACGIH) lowered the 8-hr Threshold Limit Value - time-weighted average (TLV-TWA) for toluene diisocyanate (TDI) from 5 ppb to 1 ppb, and the 15-min short-term exposure limit (STEL) from 20 ppb to 5 ppb. We evaluated ACGIH's basis for lowering these values. It is our opinion that the ACGIH's evaluation of the evidence for occupational asthma and respiratory effects from TDI exposure does not fully integrate the results of all the available human and animal studies. We found that some studies reported occupational asthma cases at TWAs less than 5 ppb, but these cases were likely caused by peak exposures above 20 ppb. Advances in industrial hygiene have reduced peak exposures and the incidence of upset conditions, such as spills and accidents, in modern TDI facilities. Taken together, the human evidence indicates that adherence to the previous 8-hr TLV-TWA and 15-min STEL (5 ppb and 20 ppb, respectively) prevents most, if not all, cases of occupational asthma, and eliminates or reduces the risk of lung function decrements and other respiratory effects. While limited, the animal literature supports the human evidence and indicates that TDI-induced asthma is a threshold phenomenon. We conclude that ACGIH's decision to lower the TLV-TWA and STEL values for TDI is not adequately supported.

Associations of symptoms related to isocyanate, ureaformol, and formophenolic exposures with respiratory symptoms and lung function in coal miners

The respiratory effects of diphenylmethane diisocyanate (MDI)-based resins and ureaformol- and formophenolic-based resins, used in coal mining, are unknown. This cross-sectional study of 354 miners evaluated respiratory health in miners with MDI-related symptoms (IS) and ureaformol/formophenolic-related symptoms (UFS). The protocol included clinical examination, chest radiograph, questionnaire on respiratory symptoms, smoking habit, job history, resin handling, and spirometry. Resin handling concerned 27.7% of the miners. IS affected 5.6%, and 1.4% also after work. UFS affected 22.6%, and 2.3% also after work. Wheezing affected 35.6%; chronic cough, expectoration, or bronchitis about 10%; dyspnea 5.4%; and asthma 2.8%. The miners with UFS had significantly more frequent chronic cough, expectoration, chronic bronchitis, dyspnea, and wheezing, whereas those with IS at and after work had markedly lower FVC, FEV1, MMEF, FEF50%, and FEF25%. These findings raise the possibility of deleterious effects of exposures to MDI and ureaformol/formophenolic resins on respiratory health and lung function in coal miners during their working life.

Science and Policy in Risk Assessments of Chlorinated Ethenes

In this article the use of data obtained from standardized experimental methods, for example, as specified in OECD guidelines for the testing of chemicals, epidemiology data, and mechanism data obtained from nonstandardized experimental methods in carcinogen risk assessment is scrutinized using the most recent risk assessments made by International Agency for Research on Cancer (IARC), the MAK(MAK)-Kommission, World Health Organization (WHO), European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC), and American Conference of Governmental Industrial Hygienists (ACGIH) for the four chlorinated ethenes as examples. The analysis shows that there was little controversy among these risk assessors about the interpretation of standardized animal data. On the other hand, they differ in their interpretation of epidemiology data, in particular in their assessment of statistical significance including the use of meta-analyses, and in quality evaluation of studies initiated on the basis of a priori concerns for carcinogenicity. The selection of mechanism data for species extrapolation is diverse among these risk assessors. Furthermore, in some cases they refrain from transparently motivating significant claims about mechanisms of toxicity by avoiding to give (explicit) references to the sources of information forming the basis of these claims or conclusions. This practice is not according to the scientific standards that should be required of a risk assessment document, and it makes it difficult to follow the argumentation and consequently to scrutinize the scientific accuracy of the conclusions drawn. In this article it is concluded that in some of these risk assessment documents, the use of mechanism data is not according to the scientific standards that should be required. It is furthermore concluded that if the use of mechanism data in these documents are representative of risk assessments in general, then there is an urgent need for further development and implementation of quality criteria for the use of mechanism data in species extrapolation.

Occurrences of Leukemia Subtypes by Socioeconomic and Occupational Groups in Sweden

OBJECTIVE

The objective of this study was to examine the associations between socioeconomic/occupational factors and histologic subtypes of leukemia.

METHODS

The Swedish Family-Cancer Database was used to calculate standardized incidence ratios for different social classes and occupational groups.

RESULTS

The overall standardized incidence ratio was close to unity between different socioeconomic groups, except for female manual workers with a significantly decreased risk. Among male occupations, increased risks were noted for sales agents, seamen, and chemical process workers. For female occupations, increased risks were observed among mechanics, iron and metalware workers, hairdressers, and launderers and dry cleaners.

CONCLUSIONS

The present study suggests that socioeconomic/occupational factors have a minor effect on the risk of leukemia. Occupational groups with possible exposure to organic solvents and other chemicals such as chemical process workers, mechanics, iron and metalware workers, and launderers and dry cleaners may entail true risk for leukemia.

Investigation of pulmonary function among employees exposed to low levels of monomeric isocyanates and solvents at an automobile finishings plant

There have been reports in the literature of decrements in pulmonary function associated with long-term, low-level monomeric isocyanate exposure combined with solvent exposure. This cross-sectional study examines the relationship between these exposures and pulmonary function in an automobile paint and coating (finishes) plant. A job exposure matrix was developed for isocyanate and solvent exposure; years in a work task were used as a surrogate for exposure. Recent pulmonary function tests were used as the outcome variables; specifically the difference between predicted and actual FEV1 and FVC. The results of the analysis demonstrated no statistically significant relationship between combined isocyanate and solvent exposure and decline in pulmonary function. There was a statistically significant negative correlation between solvent exposure and FEV1 and FVC.

A longitudinal study of respiratory health of toluene diisocyanate production workers

A longitudinal comparison of 305 toluene diisocyanate (TDI) and 581 hydrocarbons workers employed at a Texas chemical manufacturing facility from 1971 through 1997 tested whether workplace exposure to TDI was associated with changes in any of the respiratory measures collected by the company's health surveillance program. Mean TDI exposures measured 96.9 ppb-months, or 2.3 ppb per job. At the end of the study, there were no differences in self-reported symptoms between the groups. Longitudinal analyses of symptoms and pulmonary function showed no correlation with TDI exposure, yielding an average annual decrease in forced expiratory volume at 1 second of 30 mL per year. We concluded that exposure to TDI at workplace concentrations was not associated with respiratory illnesses in this cohort, and consistent with other recent research, it seemed not to accelerate the normal age-related decline in pulmonary function.

Exposure to isocyanates and organic solvents, and pulmonary-function changes in workers in a polyurethane molding process

The extent of adverse health effects of isocyanates when combined with other chemicals is not well documented. This study was conducted as a 2.5-year follow-up as well as to determine daily and weekly effects of exposure to isocyanates and organic solvents on pulmonary function. The concentrations of chemicals sampled were below the recommended exposure criteria. No daily or weekly reduction in the subjects' pulmonary function was observed. The isocyanate/solvent-exposed subjects showed significant long-term reduction in their forced vital capacity (P < 0.05) and expiratory volume in 1 second (P < 0.001). No such changes were observed in non-exposed subjects or in those exposed only to organic solvents. The proportion of subjects who developed respiratory symptoms in the isocyanate-exposed group was not significantly greater than that of the non-exposed group. The results of this study indicate that long-term exposure to isocyanates, even in very low concentrations, may contribute to impaired pulmonary function.

General mortality and respiratory cancer among a cohort of male chemical workers in California

Cohort mortality and nested case-control studies were conducted involving 2,901 men employed 1 year or more between 1940 and 1986 at any of four California facilities of a major chemical company. Employees experienced fewer deaths from each of the major causes than were expected based on U.S., California, and local county mortality rates. Respiratory cancer was significantly elevated in one socioeconomic category comprised of operators (SMR = 157, 95% CI = 109-220). The 34 cases who died from respiratory cancer and 136 matched controls, all of whom were operators, were included in a nested case-control study. Departments in which subjects had worked were grouped into 13 work assignment or product categories by an industrial hygienist without knowledge of case-control status. Smoking habits and other occupational exposures were ascertained by telephone interview from subjects or surrogate-responders. As expected, current cigarette smoking was strongly related to respiratory cancer. After adjustment for smoking, cases were significantly more likely than controls to have ever worked in one of the 13 work areas (supervision, services, and business support). However, no dose-response relationship was evident with duration of employment in this work area and the departments involved were associated with plant security and not chemical production. Results were similar when a 15-year latency period was assumed. These findings suggest that the excess of respiratory cancer mortality among operators was most likely due to differences in cigarette smoking or other factors not ascertained, rather than to a specific occupational exposure.