Maternal occupational noise exposure during pregnancy and children's early language acquisition.

INTRODUCTION: Noise exposure during pregnancy may affect a child's auditory system, which may disturb fetal learning and language development. We examined the impact of occupational noise exposure during pregnancy on children's language acquisition at the age of one. METHODS: A cohort study was conducted among women working in the food industry, as kindergarten teachers, musicians, dental nurses, or pharmacists who had a child aged <1 year. The analyses covered 408 mother-child pairs. Language acquisition was measured using the Infant-Toddler Checklist. An occupational hygienist assessed noise exposure individually as no (N = 180), low (70-78 dB; N = 108) or moderate/high exposure (>79 dB; N = 120). RESULTS: Among the boys, the adjusted mean differences in language acquisition scores were -0.4 (95% CI -2.5, 1.8) for low, and -0.7 (95% CI -2.9, 1.4) for moderate/high exposure compared to no exposure. Among the girls the respective scores were +0.1 (95% CI -2.2, 2.5) and -0.1 (95% CI -2.3, 2.2). Among the children of kindergarten teachers, who were mainly exposed to human noise, low or moderate exposure was associated with lower language acquisition scores. The adjusted mean differences were -3.8 (95% CI -7.2, -0.4) for low and -4.9 (95% CI -8.6, -1.2) for moderate exposure. CONCLUSIONS: In general, we did not detect an association between maternal noise exposure and children's language acquisition among one-year-old children. However, the children of kindergarten teachers exposed to human noise had lower language acquisition scores than the children of the non-exposed participants. These suggestive findings merit further investigation by level and type of exposure.

Parkinson's disease and occupational exposure to organic solvents in Finland: a nationwide case-control study.

OBJECTIVE: This study aimed to investigate the association between Parkinson's disease (PD) and occupational exposure to organic solvents generally and chlorinated hydrocarbons (CHC) in particular. METHODS: We assembled a Finland-wide case-control study for birth years 1930-1950 by identifying incident PD cases from the register of Reimbursement of Medical Costs and drawing two controls per case using incidence density sampling from the Population Information System, matched on sex, birth year, and residency in Finland in 1980-2014. Occupation and socioeconomic status (SES) were identified from national censuses. We assessed cumulative occupational exposures via FINJEM job-exposure matrix. Smoking was based on occupation-specific prevalence by sex from national surveys. We estimated confounder-adjusted PD incidence rate ratios (IRR) via logistic regression and evaluated their sensitivity to errors in FINJEM through probabilistic bias analysis (PBA). RESULTS: Among ever-employed, we identified 17 187 cases (16.0% potentially exposed to CHC) and 35 738 matched controls. Cases were more likely to not smoke and belong to higher SES. Cumulative exposure (CE) to CHC (per 100 ppm-years, 5-year lag) was associated with adjusted IRR 1.235 (95% confidence interval 0.986-1.547), with stronger associations among women and among persons who had more census records. Sensitivity analyses did not reveal notable associations, but stronger effects were seen in the younger birth cohort (1940-1950). PBA produced notably weaker associations, yielding a median IRR 1.097 (95% simulation interval 0.920-1.291) for CHC. CONCLUSION: Our findings imply that PD is unlikely to be related to typical occupational solvent exposure in Finland, but excess risk cannot be ruled out in some highly exposed occupations.

Lung cancer incidence among workers biologically monitored for occupational exposure to lead: a cohort study.

OBJECTIVE: Earlier studies have reported increased risks of lung, kidney and brain cancers for exposure to lead. The International Agency for Research on Cancer (IARC) Working Group evaluated inorganic lead and its compounds probably carcinogenic to humans. This study aimed to assess the association between blood lead level in occupational exposure and risk of lung cancer. METHODS: The study was based on the follow-up of lung cancer incidence during 1973-2014 among 20 729 employees biologically monitored for their occupational lead exposure in 1973-1983. Duration of employment in the monitored work was assessed using records from the Finnish Centre for Pensions; and potential confounding by other occupational carcinogens using longitudinal information on the occupation in censuses and the Finnish National Job-Exposure Matrix (FINJEM). Occupation- and gender-specific prevalence of regular tobacco smoking and the socioeconomic status were also utilized in the adjustments for potential confounding. RESULTS: Positive trends were found for the elevated blood lead levels on the lung cancer risk. Among employees with the duration of employment of ≥60 months, the relative risk (RR) of lung cancer was 1.72 [95% confidence interval (CI) 1.28-2.31] for mean blood lead 1.0-1.9 µmol/L and RR 2.63 (95% CI 1.71-4.05) for mean blood lead ≥2.0 µmol/L, compared with mean lead <0.5 µmol/L. The studied potential confounders did not explain the findings on the increased risk for lead exposure. CONCLUSIONS: The current study lends support to the findings that exposure to lead increases lung cancer risk. Increased risks were seen already at rather low blood lead levels.

Solvent exposed occupations and risk of Parkinson disease in Finland.

INTRODUCTION: Epidemiologic and toxicology studies suggest that exposure to various solvents, especially chlorinated hydrocarbon solvents, might increase Parkinson disease (PD) risk. METHODS: In a population-based case-control study in Finland, we examined whether occupations with potential for solvent exposures were associated with PD. We identified newly diagnosed cases age 45-84 from a nationwide medication reimbursement register in 1995-2014. From the population register, we randomly selected non-PD controls matched on sex, along with birth and diagnosis years (age). We included 11,757 cases and 23,236 controls with an occupation in the 1990 census, corresponding to age 40-60. We focused on 28 occupations with ≥ 5% probability of solvent exposure according to the Finnish Job Exposure Matrix. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) by logistic regression modeling, adjusting for age, sex, socioeconomic status, and smoking probability. RESULTS: Similar proportions of cases (5.5%) and controls (5.6%) had an occupation with potential exposure to any solvents. However, all occupations with a point estimate above one, and all significantly or marginally significantly associated with PD (electronic/telecommunications worker [OR = 1.63, 95% CI 1.05-2.50], laboratory assistant [OR = 1.40, 95% CI 0.98-1.99], and machine/engine mechanic [OR = 1.23, 95% CI 0.99-1.52]) entailed potential for exposure to chlorinated hydrocarbon solvents, specifically. Secondary analyses indicated exposure to polycyclic aromatic hydrocarbons and some metals might contribute to the association for mechanics. CONCLUSION: PD risk might be slightly increased in occupations with potential exposure to chlorinated hydrocarbon solvents. Confirmation is required in additional studies that adjust for other occupational exposures and smoking.

Cancer incidence among workers with blood lead measurements in two countries.

OBJECTIVE: Study carcinogenicity of inorganic lead, classified as 'probably carcinogenic' to humans by the International Agency for Research on Cancer (brain, lung, kidney and stomach). METHODS: We conducted internal and external analyses for cancer incidence in two cohorts of 29 874 lead-exposed workers with past blood lead data (Finland, n=20 752, Great Britain=9122), with 6790 incident cancers. Exposure was maximum measured blood lead. RESULTS: The combined cohort had a median maximum blood lead of 29 µg/dL, a mean first blood lead test of 1977, and was 87% male. Significant (p<0.05) positive trends, using the log of maximum blood lead, were found for brain cancer (malignant), Hodgkin's lymphoma, lung cancer and rectal cancer, while a significant negative trend was found for melanoma. Borderline significant positive trends (0.05≤p≤0.10) were found for oesophageal cancer, meningioma and combined malignant/benign brain cancer. Categorical analyses reflected these trends. Significant interactions by country were found for lung, brain and oesophageal cancer, with Finland showing strong positive trends, and Great Britain showing modest or no trends. Larynx cancer in Finland also showed a positive trend (p=0.05). External analyses for high exposure workers (maximum blood lead >40 µg/dL) showed a significant excess for lung cancer in both countries combined, and significant excesses in Finland for brain and lung cancer. The Great Britain data were limited by small numbers for some cancers, and limited variation in exposure. CONCLUSIONS: We found strong positive incidence trends with increasing blood lead level, for several outcomes in internal analysis. Two of these, lung and brain cancer, were sites of a priori interest.

Cancer mortality in an international cohort of reinforced plastics workers exposed to styrene: a reanalysis.

OBJECTIVE: To investigate the carcinogenicity of styrene by reanalysing data from a previous international cohort study of workers in the reinforced plastics industry. METHODS: Mortality from cancers of prior interest was analysed with more detailed consideration of exposure-response relations and an updated classification of leukaemias and lymphomas in data from a previous international cohort study of 37 021 reinforced plastics workers exposed to airborne styrene. RESULTS: Increased mortality from non-Hodgkin's lymphoma (NHL) was associated with the mean level of exposure to styrene in air (relative risk (RR) 2.31, 95% CI 1.29 to 4.12 per 100 ppm), but not with cumulative styrene exposure. Similar associations with mean exposure were observed for the oesophagus (RR 2.44, 95% CI 1.11 to 5.36 per 100 ppm) and pancreas (RR 1.89, 95% CI 1.17 to 3.09). Oesophageal cancer mortality was also associated with cumulative styrene exposure lagged 20 years (RR 1.16, 95% CI 1.03 to 1.31). No other cancer, including lung cancer, was associated with any indicator of styrene exposure. CONCLUSION: This reanalysis does not substantially change the conclusions of the original study with respect to NHL or lung cancer but new evidence concerning cancers of the oesophagus and pancreas merits further investigation.

Manual handling of burdens as a predictor of birth outcome-a Finnish Birth Register Study.

Background: Negative effects of manual handling of burdens on pregnancy outcomes are not elucidated in Finland. This study examines the association between perinatal outcomes and occupational exposure to manual handling of burdens. Methods: The study cohort was identified from the Finnish Medical Birth Register (MBR, 1997-2014) and information on exposure from the Finnish job-exposure matrix (FINJEM) 1997-2009. The cohort included all singleton births of mothers who were classified as 'service and care workers' representing the exposure group (n=74 286) and 'clerks' as the reference (n=13 873). Study outcomes were preterm birth (PTB) (<37 weeks), low birthweight (LBW) (<2500 g), small for gestational age (<2.5th percentile), perinatal death (stillbirth or early neonatal death within first seven days) and eclampsia. We used logistic regression analysis to calculate odds ratio (OR) and adjusted for maternal age, marital status, BMI, parity and smoking during pregnancy. Results: The risks of PTB [OR 1.16, 95% confidence interval (CI) 1.06-1.27], LBW (OR 1.12, 95% CI 1.01-1.25) and perinatal death (OR 1.51, 95% CI 1.09-2.09) were significantly higher among the high exposure group than in the reference group. All adverse outcomes were statistically insignificant among primiparous women except perinatal death (OR=1.95, 95% CI 1.13-3.39). Conclusions: The study indicates that the risk of adverse pregnancy outcomes might be more common among women that are highly exposed to occupational manual handling of burdens. The results should be interpreted with caution due to the use of occupational level exposure. Further studies with information on individual level exposure and start of maternity leave are recommended.

A pilot study on the reproductive risks of maternal exposure to magnetic fields from electronic article surveillance systems.

PURPOSE: We investigated the feasibility of a large-scale epidemiological study on reproductive effects of intermediate frequency (IF) magnetic field (MF) exposure among cashiers working near electronic article surveillance (EAS) systems. MATERIALS AND METHODS: The study cohort included 4157 women who had worked as cashiers in supermarkets with EAS devices (considered as exposed) or grocery stores without EAS devices (considered as unexposed) between 2008 and 2015. 536 births and 38 miscarriages occurred among these women during the study period, based on information from nationwide health registries. Measurements were also performed to characterize the MF exposure of cashiers. RESULTS: Cashiers were found to be exposed to 8.2 MHz MFs only when passing by the gates at short distance. Static fields of about 0.1 mT were observed at cashier's seat. Extremely low frequency MFs were higher at stores without EAS devices. No differences on the risk of miscarriage, reduced birth weight or preterm birth were observed between cashiers in different store types. CONCLUSIONS: Any further studies should attempt to include study subjects working near EAS systems that produce stronger IF MFs at kHz frequencies. Exposure to ELF MFs should be assessed as a possible confounding factor.

A cohort mortality study of lead-exposed workers in the USA, Finland and the UK.

OBJECTIVES: To investigate further whether inorganic lead is a carcinogen among adults, or associated with increased blood pressure and kidney damage, via a large mortality study. METHODS: We conducted internal analyses via Cox regression of mortality in three cohorts of lead-exposed workers with blood lead (BL) data (USA, Finland, UK), including over 88 000 workers and over 14 000 deaths. Our exposure metric was maximum BL. We also conducted external analyses using country-specific background rates. RESULTS: The combined cohort had a median BL of 26 µg/dL, a mean first-year BL test of 1990 and was 96% male. Fifty per cent had more than one BL test (mean 7). Significant (p<0.05) positive trends, using the log of each worker's maximum BL, were found for lung cancer, chronic obstructive pulmonary disease (COPD), stroke and heart disease, while borderline significant trends (0.05≤p≤0.10) were found for bladder cancer, brain cancer and larynx cancer. Most results were consistent across all three cohorts. In external comparisons, we found significantly elevated SMRs for those with BLs>40 µg/dL; for bladder, lung and larynx cancer; and for COPD. In a small subsample of the US cohort (n=115) who were interviewed, we found no association between smoking and BL. CONCLUSIONS: We found strong positive mortality trends, with increasing BL level, for several outcomes in internal analysis. Many of these outcomes are associated with smoking, for which we had no data. A borderline trend was found for brain cancer, not associated with smoking.

Paternal occupational lead exposure and offspring risks for schizophrenia.

This register-based cohort study investigated whether paternal occupational exposure to inorganic lead was related to offspring risk for schizophrenia spectrum disorder (SSD). Exposed men (n=11,863) were identified from blood lead measurements taken at the Finnish Institute of Occupational Health in 1973-1983. Data on mothers and their offspring born from 1972-1984 were obtained from the national Population Information System. Two population comparison offspring for each exposed offspring were matched on date of birth, sex and area (n=23,720). SSD cases were identified from The Finnish Hospital Discharge Register. Hazard ratios of SSD between exposed groups were analyzed using conditional proportional hazards regression, adjusted for parental history of psychoses, parental ages, language of offspring, father's employment, and father's self-employment. After 26-38years of follow up, there were no significant differences in the incidence of schizophrenia, either between the offspring of exposed (188/11,863; 1.6%) and unexposed fathers (347/23,720; 1.5%) or based on blood lead levels (adjusted hazard ratios (aHR): 0.97, CI 0.52-1.83, 1.25, CI 0.85-1.82, 0.90, CI 0.54-1.49, and 1.38, CI 0.65-2.92 for lead categories <0.5, 0.5-0.9, 1.0-1.4, and ≥1.5µmol/L, respectively, as compared to population comparison). Parental psychosis, paternal age and offspring language were associated with offspring risk. The findings suggest that paternal exposure to lead is not a risk factor for schizophrenia in offspring. However, the majority of exposed fathers had low-level exposure, and we cannot exclude the possibility of an effect for higher exposures to lead.

Selection bias due to parity-conditioning in studies of time trends in fertility.

BACKGROUND: Studies of couple fertility over time have often examined study populations with broad age ranges at a cross-section of time. An increase in fertility has been observed in studies that followed episodes of fertility events either prospectively among nulliparous women or retrospectively among parous women. Fertility has a biological effect on parity. If defined at a cross-section of time, parity will also be affected by year of birth, and thus becomes a collider. Conditioning (stratifying, restricting, or adjusting) on a collider may cause selection bias in the studied association. METHODS: A study with prospective follow-up was taken as the model to assess the validity of fertility studies. We demonstrate the potential for selection bias using causal graphs and nationwide birth statistics and other demographic data. We tested the existence of parity-conditioning bias in data including both parous and nulliparous women. We also used a simulation approach to assess the strength of the bias in populations with prior at-risk cycles. Finally, we evaluated the potential for selection bias due to conditioning on parity in various sampling frames. RESULTS: Analyses indicate that the observed increase in fertility over time can be entirely explained by selection bias due to parity-conditioning. CONCLUSION: Heterogeneity in fertility and differential success in prior at-risk cycles are the ultimate factors behind the selection bias. The potential for selection bias due to parity-conditioning varies by sampling frame. A prospective multidecade study with representative sampling of birth cohorts and follow-up from menarche to menopause would bypass the described bias.

Risk of schizophrenia and minority status: a comparison of the Swedish-speaking minority and the Finnish-speaking majority in Finland.

Approximately five percent of the Finnish population are Swedish-speaking and have higher socioeconomic position and longer life expectancy than the Finnish-speaking majority. Previous studies have not investigated whether Swedish-speaking Finns have lower risk of schizophrenia spectrum disorders (SSD) than Finnish-speaking Finns. We investigated this in a representative sample of 47 445 Finns born in 1972-1984. Hazard ratios of SSD between language groups were assessed with conditional proportional hazards regression. Sex, parental ages at birth, paternal employment around conception, parental psychosis and place and residence in the capital area were used as other explanatory variables. The prevalence of SSD was 0.7% in the Swedish-speaking minority and 1.5% in the Finnish-speaking majority. In the adjusted regression model, belonging to the Swedish-speaking minority was associated with lower risk of SSD (hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.24-0.69). In a subset analysis by gender, the protective effect was evident among Swedish-speaking males (HR 0.32, 95% CI 0.15-0.68) but marginal in females (HR 0.75, 95% CI 0.41-1.37). Parental psychosis and place of birth in the capital area were associated with higher risk of SSD, whereas paternal employment at the time of conception was associated with lower risk of SSD. Our results support the role of social factors in the etiology of schizophrenia. Belonging to a minority with high socioeconomic status and social capital may be protective against schizophrenia, especially for males.

Increased risk of human parvovirus B19 infection in day-care employees: a cohort study among pregnant workers during an epidemic in Finland.

BACKGROUND: Human parvovirus B19 (B19V) infection during early pregnancy increases the risk of miscarriage. Studies have inconsistently shown an elevated risk of infection among women with occupational contacts with children. Methodological differences, particularly in defining occupational exposure and in the type of reference group, may explain the conflicting findings. METHODS: This cohort study compared B19V infections in pregnant day-care employees and healthcare professionals during a B19V epidemic in Finland. Women were identified from the files of nationwide trade unions and the National Supervisory Authority for Welfare and Health. Early-pregnancy maternal B19V IgG was analysed in 3710 women, and infections were defined as seroconversions after analysing in parallel the available umbilical cord blood samples of the 847 seronegative mothers. Independently of the serological status, the actual employment during pregnancy was assessed using registered information on employment history. RESULTS: B19V infections were more common among day-care employees (22/331, 6.6%), than among those working in healthcare (12/326, 3.7%). The adjusted HRs of B19V infection, using proportional hazard regression, was 2.63 (95% CI 1.27 to 5.46) among all women and 5.59 (95% CI 1.40 to 22.4) among nulliparous women. CONCLUSIONS: Day-care employees are at an increased risk of B19V infection, which warrants preventive measures.

Risk of cancer among workers exposed to trichloroethylene: analysis of three Nordic cohort studies.

BACKGROUND: Trichloroethylene (TCE) is a widely used chlorinated solvent with demonstrated carcinogenicity in animal assays. Some epidemiologic studies have reported increased risk of cancer of the kidney, cervix, liver and biliary passages, non-Hodgkin lymphoma, and esophageal adenocarcinoma. METHODS: We established a pooled cohort, including 5553 workers with individual documented exposure to TCE in Finland, Sweden, and Denmark. Study participants were monitored for the urinary TCE metabolite trichloroacetic acid from 1947 to 1989 and followed for cancer. Standardized incidence ratios (SIRs) were calculated based on cancer incidence rates in the three national populations. Cox proportionate hazard analyses were used for internal comparisons. Tests of statistical significance are two-sided. RESULTS: Overall, 997 cases of cancer (n = 683 in men; n = 314 in women) were identified during 154 778 person-years of follow-up. We observed statistically significant elevated standardized incidence ratios for primary liver cancer (1.93; 95% confidence interval [CI] = 1.19 to 2.95) and cervical cancer (2.31; 95% CI = 1.32 to 3.75). The standardized incidence ratio for kidney cancer was 1.01 (95% CI = 0.70 to 1.42) based on 32 cases; we did not observe a statistically significant increased risk of non-Hodgkin's lymphoma (SIR = 1.26; 95% CI = 0.89 to 1.73) or esophageal adenocarcinoma (SIR = 1.84; 95% CI = 0.65 to 4.65). Tobacco- and alcohol-associated cancers were not statistically significantly increased. CONCLUSIONS: Our results suggest TCE exposure is possibly associated with an increased risk for liver cancer. The relationship between TCE exposure and risks of cancers of low incidence and those with confounding by lifestyle and other factors not known in our cohort require further study.

Fecundability among newly married couples in agricultural villages in Palestine: a prospective study.

BACKGROUND: The validity of studies on fecundability in Western countries has been questioned. The complexity of societal and cultural factors makes it difficult to dissect pure biological impact. Our aim was to assess couple fecundability in a population which to a large degree is unaffected by the same socio-cultural influences. METHODS: We conducted a prospective study on time-to-pregnancy (TTP), with a complete follow-up between 2005 and 2007, among 205 newly married couples in two Palestinian agricultural villages. The couples had never had premarital sex and all planned to become pregnant. We followed the couples from the date of marriage until pregnancy was recognized by a pregnancy test, or at maximum 12 months. RESULTS: Overall fecundability was 0.17. Unexpectedly, cycle fecundability increased during the first cycles from 0.16 (cycle 1) to 0.25 (cycle 5), after which the expected decline started. The initial increase in fecundability was restricted to couples with teenage brides. A total of 70.7% of the couples conceived within 6 cycles, 13.4% did not conceive during follow-up. Prolonged TTP was associated with the oldest age category for both genders. Educated women appeared to be highly fecund. CONCLUSIONS: The fecundability result is probably uninfluenced by the societal and cultural factors seen in Western populations, because premarital sex is a taboo in this Muslim population. The increase in fecundability during the first months following marriage is difficult to interpret, but could be due to either behavioural or biological influences.

Pregnancy outcomes among daycare employees in Finland.

OBJECTIVE: The aim of this study was to investigate whether working as a daycare employee increases the risk of perinatal death, pre-term birth, low birth weight, smallness for gestational age, or congenital malformations. METHODS: We conducted a register-based cohort study among daycare employees and women from various occupations of healthcare (reference group). Study subjects were identified from the files of Finnish trade unions and the National Authority for Medicolegal Affairs. Pregnancy outcomes, antenatal occupation, and working status were obtained by linkage to national registers. The final data consisted of 13 299 and 12 182 singleton births in the study and reference groups, respectively. We analyzed pregnancy outcome data using generalized estimating equations and linear regression. RESULTS: The occurrences of pre-term birth [odds ratio (OR) 0.91, 95% confidence interval (95% CI) 0.79-1.06], perinatal death (OR 0.91, 95% CI 0.62-1.34), smallness for gestational age (OR 1.01, 95% CI 0.91-1.12), and congenital malformation (OR 1.10, 95% CI 0.92-1.32) were similar among the children of the daycare employees and the reference group. The adjusted mean birth weight of the children of the daycare employees was slightly higher (14 g, 95% CI -1-29) than that of the reference group, but the difference was attenuated to 6 g in the subset of the first births. CONCLUSION: Daycare employees were not, in general, at an increased risk of an adverse pregnancy outcome. However, efforts should nevertheless be made to prevent their exposure to harmful viruses and heavy physical load during pregnancy.

Risk of liver cancer and exposure to organic solvents and gasoline vapors among Finnish workers.

We investigated the association between exposure to various groups of solvents and gasoline vapors and liver cancer. A cohort of economically active Finns born between 1906 and 1945 was followed up during the period 1971-1995. The incident cases of primary liver cancer (n = 2474) were identified in a record linkage with the Finnish Cancer Registry. Occupations from the 1970 census were converted to exposures using a job-exposure matrix. Cumulative exposure was calculated as the product of estimated prevalence, level and duration of exposure, and we used Poisson regression to calculate the relative risks (RR). Among the occupations entailing exposure to organic solvents, an elevated liver cancer incidence was observed in male printers, and varnishers and lacquerers. Among men, the risk was increased in the highest exposure category of aromatic hydrocarbons [RR 1.77, 95% confidence interval (CI) 1.30-2.40], aliphatic/alicyclic hydrocarbons (RR 1.47, 95% CI 0.99-2.18), chlorinated hydrocarbons (RR 2.65, 95% CI 1.38-5.11) and "other solvents" (RR 2.14, 95% CI 1.23-3.71). Among women, the risk was increased for the group "other solvents" that includes mainly alcohols, ketones, esters and glycol ethers (RR 2.73, 95% CI 1.21-6.16). Our finding of an increased risk among workers exposed to chlorinated hydrocarbons is in line with several earlier studies on trichloroethylene. The results also suggest a link between exposure to other types of solvents and the risk of liver cancer. The possibility that alcohol consumption contributes to the observed risks cannot be totally excluded.