Occupational Styrene Exposure Research Articles

Associations of Occupational Styrene Exposure With Risk of Encephalopathy and Unspecified Dementia: A Long-Term Follow-up Study of Workers in the Reinforced Plastics Industry.

Exposure to industrial solvents has been associated with encephalopathy. Styrene is a neurotoxic industrial solvent, and we investigated the long-term risk of encephalopathy and unspecified dementia following styrene exposure. We followed 72,465 workers in the reinforced plastics industry in Denmark (1977–2011) and identified incident cases of encephalopathy (n = 228) and unspecified dementia (n = 565) in national registers. Individual styrene exposure levels were modeled from information on occupation, measurements of work place styrene levels, product, process, and years of employment. Adjusted analyses were performed using a discrete survival function. A positive trend for encephalopathy (P < 0.01) and a negative trend for unspecified dementia (P = 0.03) were seen with cumulative styrene exposure accrued during the recent period of up to 15 years. For unspecified dementia and the combination of unspecified dementia and encephalopathy, a positive trend was indicated when applying a 30-year exposure lag (P = 0.13 and P = 0.07). The risk patterns seen following recent exposure probably reflect diagnostic criteria for encephalopathy requiring recent industrial solvent exposure and referral bias rather than association with styrene exposure, while the increasing risk observed for unspecified dementia and the combination of encephalopathy and unspecified dementia following distant exposure indicates an increased risk of dementia following styrene exposure with a long latency period.

A follow-up study of occupational styrene exposure and risk of autoimmune rheumatic diseases

ObjectivesIncreased risk has been suggested for autoimmune rheumatic diseases following solvent exposure. The evidence for specific solvents is limited, and little is known about exposure–response relations. Styrene is an aromatic,...

Lung disease associated with occupational styrene exposure.

Despite reports of pulmonary toxicity due to styrene, guidelines on acceptable styrene exposure levels have been based on risk of cancer and central nervous system and liver toxicity and not on respiratory effects. Many reports have linked exposure to styrene vapor in occupational settings to various forms of non-malignant pulmonary disorders including bronchiolitis, hypersensitivity pneumonitis, and occupational asthma. We report two cases in which the same tasks performed in a single workplace resulted in exposure to styrene vapor with subsequent development of acute respiratory symptoms associated with impaired gas exchange and imaging and histopathologic findings consistent with bronchiolitis and organizing pneumonia. Both patients gradually recovered once their workplace exposure to styrene was terminated. Clinicians, employers, and insurers should be aware of the potential for pulmonary toxicity from exposure to styrene.

Styrene Exposure and Risk of Lymphohematopoietic Malignancies in 73,036 Reinforced Plastics Workers.

Styrene is an important industrial chemical that the general population is exposed to at low levels. Previous research has suggested increased occurrence of leukemia and lymphoma among reinforced plastics workers exposed at high levels of styrene. We followed 73,036 workers of 456 small- and medium-sized Danish reinforced plastics companies from 1968 to 2011 and investigated the exposure-response relation between cumulative styrene exposure and incidence of lymphohematopoietic malignancies. We modeled styrene exposure from employment history, survey data, and historical styrene exposure measurements. We retrieved information on lymphohematopoietic malignancies from national cancer and patient registers. We identified 665 cases overall of 21 different lymphohematopoietic malignancies or combinations thereof, each with at least 20 cases, during 1,581,976 person-years of follow-up. Initial analyses suggested higher age, sex, and calendar year-adjusted incidence rate ratios (RRs) for acute myeloid leukemia, Hodgkin lymphoma, and T-cell lymphoma with higher estimates of cumulative styrene exposure. Accounting for time since exposure showed a trend by cumulative styrene exposure (P = 0.01) and a doubled risk (RR = 2.4; 95% CI, 1.2, 4.6) of acute myeloid leukemia following estimated high compared with estimated low cumulative exposure during the prior 15-29 years. We observed no increased risk following exposure during more recent years and less consistent risk patterns for Hodgkin lymphoma and T-cell lymphoma. This study, to our knowledge the largest epidemiologic study to date of occupational styrene exposure, suggests increased risk of acute myeloid leukemia following high styrene exposure with a latency period of about 15 years.

Investigating How Occupational Styrene Exposure In The Plastics Industry Could Lead To Dyschromatopsia

Investigating How Occupational Styrene Exposure In The Plastics Industry Could Lead To Dyschromatopsia

Occupational styrene exposure and acquired dyschromatopsia: A systematic review and meta-analysis.

Styrene is a chemical used in the manufacture of plastic-based products worldwide. We systematically reviewed eligible studies of occupational styrene-induced dyschromatopsia, qualitatively synthesizing their findings and estimating the exposure effect through meta-analysis. PubMed, EMBASE, and Web of Science databases were queried for eligible studies. Using a random effects model, we compared measures of dyschromatopsia between exposed and non-exposed workers to calculate the standardized mean difference (Hedges'g). We also assessed between-study heterogeneity and publication bias. Styrene-exposed subjects demonstrated poorer color vision than did the non-exposed (Hedges' g = 0.56; 95%CI: 0.37, 0.76; P < 0.0001). A non-significant Cochran's Q test result (Q = 23.2; P = 0.171) and an I2 of 32.2% (0.0%, 69.9%) indicated low-to-moderate between-study heterogeneity. Funnel plot and trim-and-fill analyses suggested publication bias. This review confirms the hypothesis of occupational styrene-induced dyschromatopsia, suggesting a modest effect size with mild heterogeneity between studies.

Occupational Styrene Exposure on Auditory Function Among Adults: ASystematic Review of Selected Workers.

A review study was conducted to examine the adverse effects of styrene, styrene mixtures, or styrene and/or styrene mixtures and noise on the auditory system in humans employed in occupational settings. The search included peer-reviewed articles published in English language involving human volunteers spanning a 25-year period (1990–2015). Studies included peer review journals, case–control studies, and case reports. Animal studies were excluded. An initial search identified 40 studies. After screening for inclusion, 13 studies were retrieved for full journal detail examination and review. As a whole, the results range from no to mild associations between styrene exposure and auditory dysfunction, noting relatively small sample sizes. However, four studies investigating styrene with other organic solvent mixtures and noise suggested combined exposures to both styrene organic solvent mixtures may be more ototoxic than exposure to noise alone. There is little literature examining the effect of styrene on auditory functioning in humans. Nonetheless, findings suggest public health professionals and policy makers should be made aware of the future research needs pertaining to hearing impairment and ototoxicity from styrene. It is recommended that chronic styrene-exposed individuals be routinely evaluated with a comprehensive audiological test battery to detect early signs of auditory dysfunction.

0117 Nonmalignant Disease Mortality among Styrene, Fibreglass, and Wood Dust Exposed Workers in the Reinforced Plastic Boatbuilding Industry

ObjectivesTo further evaluate the association of styrene, fibreglass, and wood dust exposure with non-malignant diseases, we extended follow-up through 2008 for 5203 workers exposed to styrene, fibreglass, and wood dust...

Occupational Styrene Exposure Induces Stress-Responsive Genes Involved in Cytoprotective and Cytotoxic Activities

ObjectiveThe aim of this study was to evaluate the expression of a panel of genes involved in toxicology in response to styrene exposure at levels below the occupational standard setting.MethodsWorkers in a fiber glass boat industry were evaluated for a panel of stress- and toxicity-related genes and associated with biochemical parameters related to hepatic injury. Urinary styrene metabolites (MA+PGA) of subjects and environmental sampling data collected for air at workplace were used to estimate styrene exposure.ResultsExpression array analysis revealed massive upregulation of genes encoding stress-responsive proteins (HSPA1L, EGR1, IL-6, IL-1β, TNSF10 and TNFα) in the styrene-exposed group; the levels of cytokines released were further confirmed in serum. The exposed workers were then stratified by styrene exposure levels. EGR1 gene upregulation paralleled the expression and transcriptional protein levels of IL-6, TNSF10 and TNFα in styrene exposed workers, even at low level. The activation of the EGR1 pathway observed at low-styrene exposure was associated with a slight increase of hepatic markers found in highly exposed subjects, even though they were within normal range. The ALT and AST levels were not affected by alcohol consumption, and positively correlated with urinary styrene metabolites as evaluated by multiple regression analysis.ConclusionThe pro-inflammatory cytokines IL-6 and TNFα are the primary mediators of processes involved in the hepatic injury response and regeneration. Here, we show that styrene induced stress responsive genes involved in cytoprotection and cytotoxicity at low-exposure, that proceed to a mild subclinical hepatic toxicity at high-styrene exposure.

Renal cancer risk and occupational exposure to polycyclic aromatic hydrocarbons and plastics.

To investigate whether occupational exposure to polycyclic aromatic hydrocarbons and certain plastic monomers increased renal cell carcinoma (RCC) risk. Unconditional logistic regression was used to calculate RCC risk in relation to exposure. No association between RCC risk and having ever been occupationally exposed to any polycyclic aromatic hydrocarbons or plastics was observed. Duration of exposure and average exposure also showed no association with risk. Suggestive positive associations between RCC risk and cumulative exposure to styrene (P-trend = 0.02) and acrylonitrile (P-trend = 0.06) were found. Cumulative exposure to petroleum/gasoline engine emissions was inversely associated with risk (P-trend = 0.02). Results indicate a possible association between occupational styrene and acrylonitrile exposure and RCC risk. Additional studies are needed to replicate findings, as this is the first time these associations have been reported and they may be due to chance.

Low level occupational exposure to styrene: Its effects on DNA damage and DNA repair

The present study aimed to evaluate the effects of styrene exposure at levels below the recommended standards of the Threshold Limit Value (TLV-TWA(8)) of 20 ppm (ACGIH, 2004) in reinforced-fiberglass plastics workers. Study subjects comprised 50 exposed workers and 40 control subjects. The exposed workers were stratified by styrene exposure levels, i.e. group I (<10 ppm, <42.20 mg/m(3)), group II (10-20 ppm, 42.20-84.40 mg/m(3)), and group III (>20 ppm, >84.40 mg/m(3)). The mean styrene exposure levels of exposed workers were significantly higher than those of the control workers. Biomarkers of exposure to styrene, including blood styrene and the urinary metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA), were significantly increased with increasing levels of styrene exposure, but were not detected in the control group. DNA damage, such as DNA strand breaks, 8-hydroxydeoxyguanosine (8-OHdG), and DNA repair capacity, were used as biomarkers of early biological effects. DNA strand breaks and 8-OHdG/10(5)dG levels in peripheral leukocytes of exposed groups were significantly higher compared to the control group (P<0.05). In addition, DNA repair capacity, determined by the cytogenetic challenge assay, was lower in all exposed groups when compared to the control group (P<0.05). The expression of CYP2E1, which is involved in styrene metabolism, in all styrene exposed groups, was higher than that of the control group at a statistically significant level (P<0.05). Levels of expression of the DNA repair genes hOGG1 and XRCC1 were significantly higher in all exposed groups than in the control group (P<0.05). In addition to styrene contamination in ambient air, a trace amount of benzene was also found but, the correlation between benzene exposure and DNA damage or DNA repair capacity was not statistically significant. The results obtained from this study indicate an increase in genotoxic effects and thus health risk from occupational styrene exposure, even at levels below the recommended TLV-TWA(8) of 20 ppm.

Occupational styrene exposure, colour vision and contrast sensitivity: a cohort study with repeated measurements

Associations between occupational styrene exposures and impairment of visual functions were investigated with a view to answering three questions: (1) are the published findings for colour vision deficiencies and impaired contrast sensitivity to reproduce in a new study approach, (2) if such effects exist, are they related to current or chronic exposures and (3) if effects exist, are there reductions in the effects during an exposure-free period? Workers from a boat building plant were examined in groups of current low [n = 97, mean mandelic acid (MA) + phenylglyoxylic acid (PGA) = 51 mg/g creatinine], medium (n = 115, mean = 229 mg/g creatinine) and high (n = 30, mean = 977 mg/g creatinine) level exposure to styrene. Job tenure was about 6 years. In addition, subgroups chronically exposed to low-short (n = 34, lifetime weighted mean 200 mg/g creatinine for 6 years) and high-long (n = 17, mean = 660 mg/g creatinine, 15 years) styrene levels were analysed. The examinations were carried out during normal working days and during the company holidays. Colour vision was investigated with the Lanthony desaturated panel D-15d using the colour confusion index (CCI) as a relevant variable. Contrast sensitivity was investigated with the Vistech charts VCTS 6500 using frequency-related results as well as total scores as variables. Co-variance analyses with repeated measurements and multiple linear regressions were used for statistical analysis. There was no evidence of significant associations between exposure parameters and CCI. This is true for the analyses with all participants as well as for those with the subgroups with high-long versus low-short exposure. Thus, no exposure related changes in the relevant variables were found during the exposure-free period. The analyses for contrast sensitivity show similar results. The largest portions of the variances in both tests were explained by age. German as mother tongue covered a considerable portion of the CCI variances. Education, long-term alcohol use and job tenure explain only partly significant portions of the test variances exhibited. Both acute styrene exposure levels of 40 ppm (range of standard deviation up to 54 ppm) and long term exposures to 27 ppm (range of standard deviation up to 44 ppm with higher exposure levels in the past) for a period of about 15 years were not identified as causing elevated risks for the investigated parameters of colour vision and contrast sensitivity. This statement contradicts the published results for styrene-related colour vision deficiencies but it seems to be compatible with published results for contrast sensitivity due to styrene exposure.

DNA single- and double-strand breaks by alkaline- and immuno-comet assay in lymphocytes of workers exposed to styrene

Occupational exposure to styrene was studied in 34 workers employed in the production of fiberglass-reinforced plastic sheets and compared to 29 unexposed healthy controls. We evaluated genotoxic effects induced by occupational styrene exposure in lymphocytes by alkaline version of the comet assay to detect single-strand breaks (SSBs), DNA oxidation products (formamido pyrimidine glycosilase (Fpg)- and endonuclease (Endo III)-sensitive sites) and DNA repair kinetics studies, as well as the neutral version of comet assay for DNA double-strand breaks (DSBs). An innovative aspect of this study was the use of immuno-comet assay, a new technique that recognizes DSBs with specific antibody by DAPI/FITC method. The battery of parameters included markers of external and internal exposure. Exposed workers showed significant high levels of SSBs ( p < 0.0001) and DSBs ( p < 0.0001) in neutral- and immuno-comet assay. A drastic decrease in DNA repair activity as compared to controls was observed (180 min vs. 35 min). Styrene workplace concentration significantly correlated with alkaline comet parameters (TM, p = 0.013; TI, p = 0.008), in negative with TL ( p = 0.022), and with DNA-base oxidation (TM Endo III, p = 0.048 and TI Endo III, p = 0.028). There was a significant negative correlation between urinary metabolites (MA + PGA) and TM Endo III ( p = 0.032) and TI Endo III ( p = 0.017).

Occupational styrene exposure and neurobehavioural functions: a cohort study with repeated measurements

Associations between occupational styrene exposure and cognitive as well as psychomotor functions were investigated with a view to answering three questions: (1) are the published results for neurobehavioural impairment reproducible, (2) if such effects exist, are they related to current or to chronic exposure and (3) if effects exist, are there reductions in the effects during an exposure-free period. Workers from a boat-building plant, some of whom were laminators, were investigated in groups of low (n = 83, mean mandelic acid MA + phenylglyoxylic acid PGA = 53 mg/g creatinine), medium (n = 101, 230 mg/g creat.) and high (n = 29, 928 mg/g creat.) levels of exposure to styrene. The mean job tenure was about 6 years. In addition, subgroups chronically exposed to low-short (n = 30, lifetime weighted average exposure mean 184 mg/g creat. for 6 years) and high-long (n = 16, 693 mg/g creat., 15 years) styrene levels were analyzed. The examinations were carried out during normal working days and during the company holidays. A symptom questionnaire and the tests Benton visual retention, symbol digit substitution and digit span for cognitive functions as well as choice reaction, aiming, peg board, tapping, and steadiness for psychomotor functions were administered. Co-variance analyzes with repeated measurements and linear regressions were used for statistical analysis. Co-factors were education, age, job tenure, long-term alcohol consumption, and German as mother tongue. In some cases also the activity as a laminator was considered. Symptoms were not related to exposure. The tests for cognitive functions generally revealed (all variance analyses) no exposure-related associations. Only the linear regressions of Benton test results showed significant correlation with parameters of chronic exposure which was still evident as a tendency in the work-free and exposure-free period. Most tests for psychomotor functions also revealed no relationships with exposure. However, the peg board test results showed significant correlations with chronic exposure which disappeared during holidays. The activity as a laminator--considered in addition to exposure parameters--was significant as a factor to explain the variability of psychomotor variables. Acute exposures to up to 40 ppm styrene and long-term exposures to about 27 ppm averaged over a period of 15 years were not identified as being associated with an elevated risk of developing impaired cognitive and psychomotor functions or increased symptom levels with the tests applied. This statement must be qualified by two exceptions: performances in the Benton test and in a finger dexterity test were associated with parameters of long-term exposure as a dose-response relationship, but not with current exposure.

Occupational styrene exposure and hearing loss: a cohort study with repeated measurements

Associations between occupational styrene exposure and impairment of hearing function were investigated, guided by three questions: are there hearing losses concerning high frequency and standard audiometric test? Are there dose-response relationships and measurable thresholds of effects? Are there signs of reversibility of possible effects if the workers are examined during times of improvement from their work? A group of workers from a boat building plant, some of whom were laminators, were examined in subgroups of current low (n = 99, mean mandelic acid MA + phenylglyoxylic acid PGA = 51 mg/g creatinine), medium (n = 118, mean 229 mg/g creat.) and high (n = 31, mean 970 mg/g creat.) exposure to styrene. In addition, subgroups chronically exposed to high-long (n = 17) and low-short (n = 34) styrene levels were analysed. The examinations were carried out during normal work days and during the company holidays. Hearing thresholds and transient evoked otoacoustic emissions (TEOAE) were measured. Statistics included multiple co-variance analyses with repeated measures, linear regressions, and logistic regressions. The analyses of all participants demonstrated no clear exposure effects. Particularly no sufficient proof of dose-response relationship measured against parameters of current exposure (MA + PGA, styrene/blood) and of chronic exposure (cumulative and average life time exposure resp.) was found. The analyses of groups exposed to high levels show elevated thresholds at frequencies up to 1,500 Hz among the subgroup exposed to high styrene levels (e.g. 40-50 ppm as average) for a longer period of time (e.g. more than 10 years). These participants also demonstrated signs of "improvement" at frequencies above 2,000 Hz during work holidays, when they were not exposed to styrene. A significantly elevated odds ratio for cases of hearing loss (more than 25 dB (A) in one ear, 3,000-6,000 Hz) was found among the group exposed to high levels (above 30 ppm as average) for a longer period of time (more than 10-26 years). The measurements of TEOAE did not exhibit significant results related to exposure. This study found, that chronic and intensive styrene exposure increases the hearing thresholds. At levels of about 30-50 ppm as an average inhaled styrene per work day over a period of about 15 years with higher exposure levels above 50 ppm in the past, an elevated risk for impaired hearing thresholds can be expected. The formerly published results on ototoxic effects below 20 ppm could not be confirmed. With few exceptions (at frequencies of 1,000 and 1,500 Hz) no dose-response relationship between threshold and exposure data was found. Improvements of hearing thresholds during work- and exposure-free period are possible.

D102 スチレン曝露における神経行動学的影響と代謝酵素の遺伝子多型との関連(有機溶剤中毒ほか,一般演題:口演,地方の時代の産業保健,第79回日本産業衛生学会)

D102 スチレン曝露における神経行動学的影響と代謝酵素の遺伝子多型との関連(有機溶剤中毒ほか,一般演題:口演,地方の時代の産業保健,第79回日本産業衛生学会)

Company-Level, Semi-Quantitative Assessment of Occupational Styrene Exposure when Individual Data are not Available

In epidemiological research, self-reported information about determinants and levels of occupational exposures is difficult to obtain, especially if the disease under study has a high mortality rate or follow-up has exceeded several years. In this paper, we present a semi-quantitative exposure assessment strategy for nested case-control studies of styrene exposure among workers of the Danish reinforced plastics industry when no information on job title, task or other indicators of individual exposure were readily available from cases and controls. The strategy takes advantage of the variability in styrene exposure level and styrene exposure probability across companies. The study comprised 1522 cases of selected malignancies and neurodegenerative diseases and controls employed in 230 reinforced plastics companies and other related industries. Between 1960 and 1996, 3057 measurements of styrene exposure level obtained from 191 companies, were identified. Mixed effects models were used to estimate expected styrene exposure levels by production characteristics for all companies. Styrene exposure probability within each company was estimated for all but three cases and controls from the fraction of laminators, which was reported by a sample of 945 living colleagues of the cases and controls and by employers and dealers of plastic raw materials. The estimates were validated from a subset of 427 living cases and controls that reported their own work as laminators in the industry. We computed styrene exposure scores that integrated estimated styrene exposure level and styrene exposure probability. Product (boats), process (hand and spray lamination) and calendar year period were the major determinants of styrene exposure level. Within-company styrene exposure variability increased by calendar year and was accounted for when computing the styrene exposure scores. Exposure probability estimates based on colleagues' reports showed the highest predictive values in the validation test, which also indicated that up to 67% of the workers were correctly classified into a styrene-exposed job. Styrene exposure scores declined about 10-fold from the 1960s-1990s. This exposure assessment approach may be justified in other industries, and especially in industries dominated by small companies with simple exposure conditions.

Relation between colour vision loss and occupational styrene exposure level

Aims: To investigate the relation between colour vision loss and the exposure level of styrene. Exposure level included the current exposure concentration, past cumulative exposure, and the maximum exposure level...

Time to pregnancy among male workers of the reinforced plastics industry in Denmark, Italy and The Netherlands. ASCLEPIOS.

The relationship between occupational styrene exposure and male fecundity was examined. Among 1560 Danish, Italian, and Dutch reinforced plastics workers, 220 styrene-exposed workers and 382 unexposed referents who had fathered a child were identified. A total of 768 historical styrene measurements conducted in 1970-1996 in the study companies formed the basis for semiquantitative exposure assessment in combination with measurements of urinary styrene metabolite levels. All the subjects were interviewed about work conditions and other factors potentially related to reduced fecundity. Fecundity was measured as the reported time to pregnancy (number of months a couple needed to conceive their youngest child). A statistically nonsignificantly reduced fecundity was observed for the styrene-exposed workers [fecundity ratio 0.79, 95% confidence interval (95% CI) 0.59-1.05]. But no consistent pattern of a detrimental effect on fecundity was found when time to pregnancy was related to worktasks indicating higher styrene exposure levels or semiquantitative or quantitative measures of styrene exposure. The workers with high exposure showed a fecundity ratio of 1.09 (95% CI 0.69-1.72). It is unlikely that styrene exposure has a strong effect on male fecundity.

Change in semen quality and sperm chromatin structure following occupational styrene exposure

Organic solvents have been suspected to exert detrimental effects on human spermiogenesis. Styrene, which is both mutagenic and neurotoxic, was selected as a suitable organic solvent for further assessment of a possible effect on semen quality and sperm DNA damage. Semen samples were collected from 23 reinforced plastics workers at the time of employment and after 6 months of styrene exposure and from 21 nonexposed farmers. Intra-individual changes in conventional semen parameters and sperm-DNA denaturation patterns were related to the internal dose of styrene exposure as measured by postshift urinary mandelic acid. A statistically significant decline in sperm density was seen during styrene exposure from 63.5 to 46.0 million sperm/ml, whereas no decline was seen in the nonexposed subjects. The total sperm count was almost halved from an initial value of 175 million sperm/ejaculate. However, no relationship was apparent when the sperm parameters were related to internal levels of exposure. However, an exposure-response relationship was shown for DNA-denaturation patterns, but the numbers were small. A declining sperm count following styrene exposure is suggested. However, the findings of the internal and external comparisons are inconsistent, and this may be due to the high intraindividual variability of semen parameters and the limited study size but may also be attributable to a weak internal exposure gradient. Spermatogenesis may be vulnerable to styrene exposure. However, due to the small numbers these findings are only preliminary.