Chemical exposures at work in early pregnancy and congenital defect: a case-referent study.

Three hundred and one women who in their most recent pregnancy had given birth to an infant with an important congenital defect were individually matched with 301 women whose children were normal. Both cases and referents were drawn from a comprehensive survey of pregnancies in Montreal, 1982-4, and limited to women employed 30 or more hours a week until at least the 13th week of gestation. Occupational exposure to chemicals was investigated and the results classified without knowledge of case-referent status. In matched pair analysis the overall frequency of chemical exposure was higher in cases than referents (63:47), due to excesses in the cardiac and miscellaneous defect groups (ratios of 10:5 and 15:7 respectively). In analyses by nine chemical categories only exposure to aromatic solvents showed a clear excess (18:8; p approximately equal to 0.04), most evident in the urinary tract group (9:0). A comparison of cases and referents exposed to aromatic solvents showed that most of the excess was associated with toluene; the defects were varied but predominantly renal-urinary or gastrointestinal.     

Primary liver cancer and exposure to solvents

Summary A case-referent study was done on the possible association between primary liver cancer (ICD 155.0) and occupational exposures. In all, 374 cases were reported to the Finnish Cancer Registry in 1979 and 1980. After the exclusion of wrong diagnoses, nonrespondents and cases for whom the primary site was uncertain, 126 cases (64 men and 62 women) remained. Each case was matched for sex, age (± 5 years), vital status and geographical district with two cases of coronary infarction selected from hospital records without any knowledge of occupational history. Nonrespondence (38%) reduced the number to 175 referents (82 men and 92 women). A questionnaire on former employment and tasks was mailed to living subjects (6+6) and to the next of kin of deceased patients. An industrial hygienist then evaluated the exposure history blindly and, whenever necessary, contacted the workplace or the next of kin for more details. Only exposures commencing 10 years or more before diagnosis were considered. Altogether six female cases but no referent had been exposed to solvents. One had been exposed to chlorinated solvents in dry cleaning and two others had used both carbon tetrachloride and aromatic and aliphatic solvents. Three cases had been exposed to mixtures of aliphatic and aromatic solvents, but not chlorinated hydrocarbons. By contrast, the men did not differ with regard to exposure to solvents. Two cases and five referents were classified as having been exposed to solvent mixtures. The present results are hypothesis generating only, and the excess solvent exposure found for women must be confirmed in other studies before any conclusions can be drawn.Part of the results have been presented at the third Conference on Epidemiology in Occupational Health, 28–30 September, 1983 in Singapore     

Renal disease and occupational exposure to organic solvents: a case referent approach.

Several recent studies have suggested that a relation may exist between exposure to occupational organic solvents and diseases of the kidney--particularly malignancy and glomerulonephritis. Two case referent studies were undertaken in the West Midlands to investigate these possibilities. In the case of renal cancer 54 live cases of biopsy proved adenocarcinoma of the kidney were compared with an equal number of community based healthy referents matched for age, sex, place of residence, and socioeconomic and ethnic grouping. For glomerulonephritis, 50 biopsy proved cases were matched in the same manner with 50 referents. Fourteen other patients were also reviewed who, on biopsy, proved not to have glomerulonephritis. For both sets of cases and their referents each individual was interviewed and a detailed account obtained of medical history and environmental exposures. Exposure to solvents was assessed independently and "blind" in a semiquantitative way by an experienced occupational hygienist. Past exposure was estimated for 10 different solvent types and 17 material types. No relation was found between exposure to solvents and renal cancer or glomerulonephritis. In the case of renal cancer the numbers studied only precluded a fourfold excess risk. For glomerulonephritis, the study, although methodologically superior to most other published studies and of similar size, was of similar power to the renal cancer investigation.     

Renal disease and occupational exposure to organic solvents: a case referent approach

Several recent studies have suggested that a relation may exist between exposure to occupational organic solvents and diseases of the kidney--particularly malignancy and glomerulonephritis. Two case referent studies were undertaken in the West Midlands to investigate these possibilities. In the case of renal cancer 54 live cases of biopsy proved adenocarcinoma of the kidney were compared with an equal number of community based healthy referents matched for age, sex, place of residence, and socioeconomic and ethnic grouping. For glomerulonephritis, 50 biopsy proved cases were matched in the same manner with 50 referents. Fourteen other patients were also reviewed who, on biopsy, proved not to have glomerulonephritis. For both sets of cases and their referents each individual was interviewed and a detailed account obtained of medical history and environmental exposures. Exposure to solvents was assessed independently and "blind" in a semiquantitative way by an experienced occupational hygienist. Past exposure was estimated for 10 different solvent types and 17 material types. No relation was found between exposure to solvents and renal cancer or glomerulonephritis. In the case of renal cancer the numbers studied only precluded a fourfold excess risk. For glomerulonephritis, the study, although methodologically superior to most other published studies and of similar size, was of similar power to the renal cancer investigation.     

Occupational risk factors for renal cell carcinoma: agent-specific results from a case-control study in Germany. MURC Study Group. Multicenter urothelial and renal cancer study

BACKGROUND: This case-control study was conducted to estimate the renal cell cancer (RCC) risk for exposure to occupation-related agents, besides other suspected risk factors. METHODS: In a population-based multicentre study, 935 incident RCC cases and 4298 controls matched for region, sex, and age were interviewed between 1991 and 1995 for their occupational history and lifestyle habits. Agent-specific exposure was expert-rated with two job-exposure matrices and a job task-exposure matrix. Conditional logistic regression was used to calculate smoking adjusted odds ratios (OR). RESULTS: Very long exposures in the chemical, rubber, and printing industries were associated with risk for RCC. Males considered as 'substantially exposed to organic solvents' showed a significant excess risk (OR = 1.6, 95% CI : 1.1-2.3). In females substantial exposure to solvents was also a significant risk factor (OR = 2.1, 95% CI : 1.0-4.4). Excess risks were shown for high exposure to cadmium (OR = 1.4, 95% CI : 1.1-1.8, in men, OR = 2.5, 95% CI : 1.2-5.3 in women), for substantial exposure to lead (OR = 1.5, 95% CI : 1.0-2.3, in men, OR = 2.6, 95% CI : 1.2-5.5, in women) and to solder fumes (OR = 1.5, 95% CI : 1.0-2.4, in men). In females, an excess risk for the task 'soldering, welding, milling' was found (OR = 3.0, 95% CI : 1.1-7.8). Exposure to paints, mineral oils, cutting fluids, benzene, polycyclic aromatic hydrocarbons, and asbestos showed an association with RCC development. CONCLUSIONS: Our results indicate that substantial exposure to metals and solvents may be nephrocarcinogenic. There is evidence for a gender-specific susceptibility of the kidneys.     

Renal cell cancer and occupational exposure to chemical agents

A case-referent study of occupational risk indicators of renal cell adenocarcinoma was conducted. Each incident case in Finland in 1977-1978 was matched with two population referents. Lifelong job histories were collected and translated into indicators of industry, occupation, and occupational exposures. The analyses of 338 sets of cases and referents revealed elevated risks for a history of employment in white-collar occupations; the printing industry; the chemical industry; the manufacturing of metal products; mail, telephone, and telegraph services; and iron and metalware work. A decreased risk was observed for male farmers. An elevated risk and an exposure-response relationship were found for gasoline exposure. The excess risk was highest at a latency period of approximately 30 years. The findings support the hypothesis that exposure to some constituent(s) of gasoline increases the incidence of renal adenocarcinoma in humans. Suggestions of elevated risks appeared for exposures to inorganic lead, cadmium, and nonchlorinated solvents.     

Normal serum activities of liver enzymes in Swedish paint industry workers with heavy exposure to organic solvents

The serum activities of the liver enzymes alanine aminotransferase, aspartate aminotransferase, ornithine carbamyl transferase, and gamma-glutamyl transferase were examined in 47 paint industry workers and unexposed age matched referents. The workers were exposed to a mixture of industrial solvents, of which xylene was the main component in most cases. The median total exposure was about 50% of Swedish 1981 threshold limit values according to measurements of individual solvent exposure performed at the same time. No differences in enzyme activities were shown either when the whole exposed and referent groups were compared or when the five workers with outstanding solvent exposures of five times the TLV or more were compared with their referents. It is concluded that in most workers the liver seems to remain largely undamaged from inhalation exposure to a commonly used mixture of non-chlorinated solvents. In many workers this seems to hold true even for high exposures for limited periods.     

Normal serum activities of liver enzymes in Swedish paint industry workers with heavy exposure to organic solvents.

The serum activities of the liver enzymes alanine aminotransferase, aspartate aminotransferase, ornithine carbamyl transferase, and gamma-glutamyl transferase were examined in 47 paint industry workers and unexposed age matched referents. The workers were exposed to a mixture of industrial solvents, of which xylene was the main component in most cases. The median total exposure was about 50% of Swedish 1981 threshold limit values according to measurements of individual solvent exposure performed at the same time. No differences in enzyme activities were shown either when the whole exposed and referent groups were compared or when the five workers with outstanding solvent exposures of five times the TLV or more were compared with their referents. It is concluded that in most workers the liver seems to remain largely undamaged from inhalation exposure to a commonly used mixture of non-chlorinated solvents. In many workers this seems to hold true even for high exposures for limited periods.     

Nasal and sinonasal cancer. Connection with occupational exposures in Denmark, Finland and Sweden

A joint Danish-Finnish-Swedish case-referent investigation was initiated in 1977 in order to study the connection between nasal and sinonasal cancer and various occupational exposures. All new cases of nasal and sinonasal cancer were collected from the national cancer registers (Finland and Sweden) or from the hospitals (Denmark). Those still alive who agreed to an interview (N = 167) were individually matched for age and sex with patients with colonic or rectal cancer. A detailed telephone interview was made according to standardized forms. Both cases and referents thought that their condition was the one under study. The exposures were coded blindly by an industrial hygienist. The results showed associations between nasal and sinonasal cancer and exposure to (i) hardwood or mixed wood dust (discordant pairs 14: 2), (ii) softwood dust alone (13:4), (iii) chromium (16: 6), (iv) nickel (12: 5, not significant), (v) welding, flame-cutting and soldering (17: 6), and (vi) lacquers and paints (14: 0). The last finding was probably due to confounding from wood dust exposure. Hardwood dust exposure was associated with adenocarcinoma. Softwood dust exposure alone was associated with epidermoid and anaplastic carcinomas. No associations were found for a number of exposures, including agricultural chemicals, textile dust, asbestos, quartz dust, organic solvents and leather work. Possible exposure to formaldehyde was evenly distributed between the cases and referents.     

Falls and fractures in women at work

BACKGROUND: Older women have been observed to have more serious injury particularly fractures after slips, trips or falls at the workplace. It is unclear whether this excess reflects a greater likelihood of falling or a greater proportion presenting with fractures once the fall has occurred. METHODS: Two studies were carried out: Study A, of 130 women who fell at work and matched referents, and Study B, of 120 women who fell at work and sustained a major fracture and 314 matched referents who fell but for whom no fracture was recorded. In Study A, the workplace of the case and referent was observed, questionnaires completed and objective health measures carried out. Study B relied on information obtained from the subject by postal questionnaire. RESULTS: Women who fell were older than referents matched on workplace and occupation, but age did not continue to be a significant factor after allowing for bodyweight and use of spectacles. Fractures were more common in older women who fell, particularly post-menopausal women with low body mass. The risk of fracture increased steadily with age without an obvious discontinuity around the likely age of menopause. CONCLUSIONS: The observed excess of fractures in older women falling at work appeared to be explained by the greater risk of fracture among those who fell.     

Occupational risk factors for urothelial carcinoma: agent-specific results from a case-control study in Germany. MURC Study Group. Multicenter Urothelial and Renal Cancer

BACKGROUND: This multicentre population-based case-control study was conducted to estimate the urothelial cancer risk for occupational exposure to aromatic amines, polycyclic aromatic hydrocarbons (PAH), and chlorinated hydrocarbons besides other suspected risk factors. METHODS: In a population-based multicentre study, 1035 incident urothelial cancer cases and 4298 controls matched for region, sex, and age were interviewed between 1991 and 1995 for their occupational history and lifestyle habits. Exposure to the agents under study was self-assessed as well as expert-rated with two job-exposure matrices and a job task-exposure matrix. Conditional logistic regression was used to calculate smoking adjusted odds ratios (OR) and to control for study centre and age. RESULTS: Urothelial cancer risk following exposure to aromatic amines was only slightly elevated. Among males, substantial exposures to PAH as well as to chlorinated solvents and their corresponding occupational settings were associated with significantly elevated risks after adjustment for smoking (PAH exposure, assessed with a job-exposure matrix: OR = 1.6, 95% CI: 1.1-2.3, exposure to chlorinated solvents, assessed with a job task-exposure matrix: OR = 1.8, 95% CI: 1.2-2.6). Metal degreasing showed an elevated urothelial cancer risk among males (OR = 2.3, 95% CI: 1.4-3.8). In females also, exposure to chlorinated solvents indicated a urothelial cancer risk. Because of small numbers the risk evaluation for females should be treated with caution. CONCLUSIONS: Occupational exposure to aromatic amines could not be shown to be as strong a risk factor for urothelial carcinomas as in the past. A possible explanation for this finding is the reduction in exposure over the last 50 years. Our results strengthen the evidence that PAH may have a carcinogenic potential for the urothelium. Furthermore, our results indicate a urothelial cancer risk for the use of chlorinated solvents.     

Lung dust analysis in the assessment of past exposure of man-made mineral fibre workers

In the cohort of American MMMF workers reported by ENTERLINE et al. [Ann. occup. Hyg. 31, 625-656 (1987)] autopsies were recorded in 652 (13.5%) of 4840 deaths. Lung tissue samples were sought from all pathologists and obtained in 145 (22.2%), together with similar samples from 124 matched referents. Lung fibre counts by phase contrast microscopy were 60% higher (P less than 0.05) in workers than referents. Electron microscopy (ATEM) also showed more fibres of all kinds--MMMF, asbestos and other--but no convincing excess of any one type. Lung samples of only 26% of workers contained any MMMF, almost all siliceous in nature and in low concentration. There were too few cases of lung cancer (19) for any useful conclusion; however, in the plant with the highest lung cancer SMR (200), and a probable mesothelioma, amosite at greater than 1.0 fibres per micrograms (f micrograms-1) was found in four of six workers but in none of their matched referents. Although our findings contribute little to the interpretation of the results obtained by ENTERLINE et al. they indicate the potential value of tissue analyses in monitoring epidemiological studies of MMMF exposure.     

Systemic sclerosis and occupational risk factors: a case-control study

Aims: A case–control study was carried out between 1998 and 2000 to investigate the relation between systemic sclerosis and occupational exposure.

Methods: Eighty cases of systemic sclerosis admitted consecutively to the Department of Internal Medicine at the University Hospital of Tours from 1998 to 2000 were included. For each case, two age, gender, and smoking habits matched controls hospitalised during the same period in the same department were selected. A committee of experts was set up retrospectively to assess occupational exposure. Exposure to silica dust and organic solvents (such as trichlorethylene and other chlorinated solvents, and benzene and other aromatic solvents) was investigated using semiquantitative estimates of exposure. An exposure score was calculated for each subject based on probability, intensity, daily frequency, and duration of exposure for each period of employment. The final cumulative exposure score was obtained, taking into account all periods of employment.

Results: Significant associations with SS were observed for crystalline silica, trichlorethylene, chlorinated solvents, toluene, aromatic solvents, ketones, white spirit, epoxy resins, and welding fumes. Risk of SS was significantly associated with a high final cumulative exposure score of occupational exposure to crystalline silica, trichlorethylene, chlorinated solvents, welding fumes, and any types of solvents.

Conclusion: Results confirm the influence of occupational risk factors in the occurrence of SS in both men and women. The link is not only with silica but also with other compounds such as solvents.

     

Maternal occupational exposure and congenital malformations.

A case-referent study was conducted to assess the risk of congenital malformations in relation to maternal occupational exposure before and during pregnancy. Three hundred and twenty-five cases of major malformations and 325 normal (at birth) referents identified in 15 maternity hospitals were included in the study. The occupational history obtained from an interview of the mother was blindly reviewed by an industrial hygienist who assessed the presence of chemical exposure and the probability of exposure. The results suggested that mothers of the case children with oral clefts were more often exposed to solvents during pregnancy [odds ratio (OR) 7.9, 90% confidence interval (90% CI) 1.8-44.9] and worked more often as cleaners (four cases, no referents). Digestive anomalies (OR 11.9, 90% CI 2.0-149) and multiple anomalies (OR 4.5, 90% CI 1.4-16.9) were also associated with occupational exposure to solvents at work. These results were not modified when differences in maternal age, area of residence, and socioeconomic status were taken into account.     

Congenital defects and work in pregnancy.

The risk of congenital defect was examined in 47,913 pregnancies of women employed for 15 hours a week or more at time of conception. The rate of defects of all types per 1000 births in this series was 25.0; 1.8 from defects classified as chromosomal (group A), 10.8 as developmental (group B), and 12.5 as musculoskeletal (group C). Some evidence of an excess in the risk ratio (p less than 0.05) was found in the services sector and in four occupations--agriculture and horticulture (2.61), telephone and postal clerks (1.74), a miscellaneous group of service jobs (1.68), and receptionists and information clerks (1.47); excesses of lower statistical significance (p less than 0.1) were found in those engaged in plastics and rubber manufacture (2.02) and in child minders (1.84). There were two cases of tracheo-oesophageal fistula--a rare defect--among eight defects (1.32 expected) in agriculture and horticulture. Overall, the distribution of risk ratios in the 60 occupations examined was not significantly heterogeneous. Analysis of chemical exposure profiles for each occupational group showed no evidence of any increased risk, perhaps due to lack of sensitivity and discrimination in this method of exposure estimation. In 152 pregnancies of doctors and nurses who had administered antineoplastic drugs in the first month eight defects, miscellaneous in type, were observed compared with 4.05 expected (p = 0.05). Special study of musculoskeletal defects and work demands showed some evidence of an association with a long working week (greater than or equal to 46 hours) but no other ergonomic factor. With these few exceptions the survey failed to identify appreciable risk of congenital defect related to occupation.     

Congenital defects and work in pregnancy

The risk of congenital defect was examined in 47,913 pregnancies of women employed for 15 hours a week or more at time of conception. The rate of defects of all types per 1000 births in this series was 25.0; 1.8 from defects classified as chromosomal (group A), 10.8 as developmental (group B), and 12.5 as musculoskeletal (group C). Some evidence of an excess in the risk ratio (p less than 0.05) was found in the services sector and in four occupations--agriculture and horticulture (2.61), telephone and postal clerks (1.74), a miscellaneous group of service jobs (1.68), and receptionists and information clerks (1.47); excesses of lower statistical significance (p less than 0.1) were found in those engaged in plastics and rubber manufacture (2.02) and in child minders (1.84). There were two cases of tracheo-oesophageal fistula--a rare defect--among eight defects (1.32 expected) in agriculture and horticulture. Overall, the distribution of risk ratios in the 60 occupations examined was not significantly heterogeneous. Analysis of chemical exposure profiles for each occupational group showed no evidence of any increased risk, perhaps due to lack of sensitivity and discrimination in this method of exposure estimation. In 152 pregnancies of doctors and nurses who had administered antineoplastic drugs in the first month eight defects, miscellaneous in type, were observed compared with 4.05 expected (p = 0.05). Special study of musculoskeletal defects and work demands showed some evidence of an association with a long working week (greater than or equal to 46 hours) but no other ergonomic factor. With these few exceptions the survey failed to identify appreciable risk of congenital defect related to occupation.     

Influence of solvent exposure and aging on cognitive functioning: an 18 year follow up of formerly exposed floor layers and their controls

Objectives: To extend our knowledge of how exposure to neurotoxic substances during working life affects cognitive functioning in the long term. Does long term occupational exposure to organic solvents lead to aggravated cognitive impairment later in life? Methods: A follow up was conducted of floor layers exposed to solvents and their unexposed referents (carpenters) 18 years after the baseline assessment. The pattern of cognitive changes in the two groups was compared, with the same 10 neuropsychological tests from the test battery for investigating functional disorders (TUFF) that were used at baseline. The study included 41 floor layers and 40 carpenters. A medical examination focused on health at the present and during the past 18 years. An extensive exposure assessment made in the initial study included questionnaires, interviews, and measurements. Additional exposure during the follow up period was minor, as explored in interviews at follow up. Results: The entire group of floor layers did not deteriorate significantly more over time than did the carpenters. However, among the oldest subjects (>60 years), only floor layers showed decline in visual memory. Moreover, the most highly exposed floor layers deteriorated significantly more than their referents in visual memory and perceptual speed, and they tended to display larger decrements in motor speed. Significant dose effect relations were found; higher cumulative exposure was associated with decrements in visual episodic memory, perceptual speed and attention, and visuospatial skill. Conclusions: The hypothesis that floor layers would deteriorate more in cognitive performance than their unexposed referents over a period of 18 years was partly supported by the results of this study. The results are consistent with the view that the negative effects of exposure to solvents may interact with the normal aging process, primarily at heavy exposure.     

Identification of occupational cancer risks in British Columbia. A population-based case-control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors

Lifetime occupational histories as well as information on known and suspected breast cancer risk factors were collected by means of a self-administered questionnaire from 1018 women with incident breast cancer ascertained from the British Columbia Cancer Registry, and from 1020 population controls. A matched case-control study design was used. Conditional logistic regression for matched sets data and the likelihood ratio were used in a two-step procedure and were performed separately for pre-menopausal women, post-menopausal women, and for all cases combined. Excess risk was noted for several white-collar occupations. Significantly increased risk was observed: (1) among pre-menopausal women: in electronic data-processing operators; barbers and hairdressers; in sales and material processing occupations; and in the food, clothing, chemical and transportation industries; (2) among post-menopausal women: in schoolteaching; in medicine, health, and nursing occupations; in laundry and dry-cleaning occupations; and in the aircraft and automotive, including gasoline service station, industries. Several significant associations were also seen in the combined group of pre- and post-menopausal women, particularly in crop farmers and in the fruit and vegetable, publishing and printing, and motor vehicle repair industries. The results of this study suggest excess breast cancer risk in a number of occupations and industries, notably those that entail exposure to solvents and pesticides.     

Increased risk for primary liver cancer among women exposed to solvents

An earlier case-referent study by the same authors [Int Arch Occup Environ Health 54 (1984) 147-153] reported that solvent-exposed women, but not men, had an increased risk for primary liver cancer. The present study was undertaken to verify these results. The relatives of deceased patients, ie, 377 liver cancer cases, 385 coronary infarction referents, and 476 stomach cancer referents, responded to a questionnaire on past employment and potentially relevant covariables, the response rates being 71.7, 72.7, and 69.0%, respectively. The information was assessed for solvent exposure by two occupational hygienists without knowledge of the patients' diagnoses. Seven male and seven female liver cancer cases had been exposed to solvents, the odds ratio being less than 1 for the men but greater than 3 for the women irrespective of the reference group used for comparison. The results confirm the authors' earlier findings. When both materials were combined, the odds ratio was 7.8 for the female liver cancer cases as compared with the infarction referents. In the combined material, nine female liver cancer cases, two stomach cancer referents, but no infarction referent had had at least probable exposure to chlorinated hydrocarbons. Such exposure was rare among all of the men in the study. This finding may explain why the increased liver cancer risk occurred only for the women, although a sex difference in sensitivity cannot be completely ruled out.     

Maternal occupational exposure to chemical substances and the risk of infants small-for-gestational-age.

BACKGROUND: The association between maternal occupational exposure to specific chemical substances (organic solvents, carbon tetrachloride, herbicides, chlorophenols, polychlorinated biphenyls, aromatic amines, lead and lead compounds, mercury and mercury compounds) and birth of small-for-gestational-age (SGA) infants was evaluated using data from a prospective cohort study of 3,946 pregnant women in West Germany from 1987 to 1988. METHODS: Occupational, medical, and psychosocial information was gathered through a questionnaire from pregnant women who were recruited between 15 and 28 gestational weeks. Exposure to chemical substances at the current workplace was assessed by a job-exposure matrix constructed by Pannett in 1985 and weighted for the number of working hours per week. Women not working at the time of the interview, women with multiple births, and women with stillbirths were excluded from analysis. Data were analyzed using dichotomous and polytomous logistic regression to control for age, smoking status, alcohol consumption, body mass index, and number of former births. RESULTS: The results of the dichotomous logistic regression analysis suggest that leather work might be associated with the birth of infants small-for-gestational-age through exposure to chlorophenols (P = 0.02) and aromatic amines (P = 0.05). In the polytomous logistic regression analysis, only the association between exposure to mercury and growth retardation reached statistical significance (P = 0.02); however, the power of the study is limited. Further adjustment for income, shift work, and heavy physical work had no substantial effect on the results. CONCLUSIONS: These findings suggest that maternal exposure to specific chemicals at work may be a risk factor for the birth of SGA infants.