Maternal occupational exposure to electromagnetic fields before, during, and after pregnancy in relation to risks of childhood cancers: findings from the Oxford Survey of Childhood Cancers, 1953-1981 deaths

BACKGROUND: The concern that maternal exposure to electromagnetic fields (EMF) might be related to childhood cancer risks, particularly leukemia risks. METHODS: Maternal occupational data already collected as part of the Oxford Survey of Childhood Cancers have been reviewed. Information on occupations held before, during, and after the pregnancy was sought for 15,041 children dying of cancer in Great Britain in the period 1953-1981, and for an equal number of matched controls. Each period of working was classified under one of five headings: (1) sewing machinist; (2) textile industry workers (other than sewing machinists) with likely exposures to EMF; (3) other machinists and other jobs with likely "higher" EMF exposure; (4) other jobs with likely exposure to some EMF, and (5) jobs with little potential for EMF exposure. RESULTS: Relative to risks in the children of mothers who held occupations with little potential for EMF exposure during pregnancy (a category that included housewives), risks of all childhood cancers were close to unity both for the children of sewing machinists (22 case and 31 control mothers, RR 0.72, 95% CI 0.42 to 1.25) and for the children of other machinists with likely "higher" EMF exposures (44 case and 47 control mothers, RR 0.93, 95% CI 0.61 to 1.41). Corresponding risks for all childhood leukemias and for all childhood brain cancers were similarly unexceptional. Simultaneous adjustment for social class, maternal age at birth of child, and sibship position had little effect. CONCLUSIONS: The study findings did not indicate that maternal occupational exposure to EMF during pregnancy is a risk factor for childhood leukemias, childhood brain cancers, or the generality of all childhood cancers.     

Paternal occupational exposures and childhood cancer

The objective of the study described here was to test the hypothesis that paternal occupational exposure near conception increases the risk of cancer in the offspring. We conducted a cohort study based on a population of 235,635 children born shortly after two different censuses in Sweden. The children were followed from birth to 14 years, and cases of cancer were identified in the Swedish Cancer Registry. Occupational hygienists assessed the probability of exposure to different agents in each combination of the father's industry and occupation as reported in the censuses. We also analyzed individual job titles. We compared the cancer incidence among children of exposed fathers to that among children of unexposed fathers using Cox proportional hazards modeling. The main findings were an increased risk of nervous system tumors related to paternal occupational exposure to pesticides [relative risk (RR) = 2.36; 95% confidence interval (CI), 1.27-4.39] and work as a painter (RR = 3.65; 95% CI, 1.71-7.80), and an increased risk of leukemia related to wood work by fathers (RR = 2.18; 95% CI, 1.26-3.78). We found no associations between childhood leukemia and paternal exposure to pesticides or paint. Our results support previous findings of an increased risk of childhood brain tumors and leukemia associated with certain paternal occupational exposures. Some findings in previous studies were not confirmed in this study.     

Parental occupational exposure to pesticides and childhood germ-cell tumors

In a recently completed US case-control study (Children's Oncology Group, 1993-2001) with 253 cases and 394 controls, the authors investigated the association between parental occupational exposure to pesticides and risk of childhood germ-cell tumors. Information on occupational pesticide exposure was collected using job-specific module questionnaires and assessed by an experienced industrial hygienist. Odds ratios for childhood germ-cell tumors associated with maternal exposures before pregnancy, during pregnancy, and after the birth of the index child were 1.0 (95% confidence interval (CI): 0.8, 1.4), 1.1 (95% CI: 0.7, 1.6), and 1.3 (95% CI: 0.9, 1.8), respectively. Paternal exposures before pregnancy, during pregnancy, and after the birth of the index child were not related to germ-cell tumors (odds ratios (ORs) were 0.9 (95% CI: 0.7, 1.2), 0.8 (95% CI: 0.5, 1.2), and 0.8 (95% CI: 0.5, 1.3), respectively). When both parents had ever been occupationally exposed to pesticides before the index pregnancy, the odds ratio was 0.8 (95% CI: 0.4, 1.3). Subgroup analyses showed a positive association between maternal exposure to herbicides during the postnatal period and risk of germ-cell tumors in girls (OR = 2.3, 95% CI: 1.0, 5.2) and an inverse association between paternal exposure to pesticides during the index pregnancy and germ-cell tumors in boys (OR = 0.2, 95% CI: 0.1, 1.0). This study did not provide strong evidence supporting a relation between parental pesticide exposure in the workplace and risk of germ-cell tumors among offspring.     

Critical windows of exposure to household pesticides and risk of childhood leukemia

The potential etiologic role of household pesticide exposures was examined in the Northern California Childhood Leukemia Study. A total of 162 patients (0-14 years old) with newly diagnosed leukemia were rapidly ascertained during 1995-1999, and 162 matched control subjects were randomly selected from the birth registry. The use of professional pest control services at any time from 1 year before birth to 3 years after was associated with a significantly increased risk of childhood leukemia [odds ratio (OR) = 2.8; 95% confidence interval (CI), 1.4-5.7], and the exposure during year 2 was associated with the highest risk (OR = 3.6; 95% CI, 1.6-8.3). The ORs for exposure to insecticides during the 3 months before pregnancy, pregnancy, and years 1, 2, and 3 were 1.8 (95% CI, 1.1-3.1), 2.1 (95% CI, 1.3-3.5), 1.7 (95% CI, 1.0-2.9), 1.6 (95% CI, 1.0-2.7), and 1.2 (95% CI, 0.7-2.1), respectively. Insecticide exposures early in life appear to be more significant than later exposures, and the highest risk was observed for exposure during pregnancy. Additionally, more frequent exposure to insecticides was associated with a higher risk. In contrast to insecticides, the association between herbicides and leukemia was weak and nonsignificant. Pesticides were also grouped based on where they were applied. Exposure to indoor pesticides was associated with an increased risk, whereas no significant association was observed for exposure to outdoor pesticides. The findings suggest that exposure to household pesticides is associated with an elevated risk of childhood leukemia and further indicate the importance of the timing and location of exposure.     

Potential residential exposure to toxics release inventory chemicals during pregnancy and childhood brain cancer

BACKGROUND: Although the susceptibility of the developing fetus to various chemical exposures is well documented, the role of environmental chemicals in childhood brain cancer etiology is not well understood. OBJECTIVES: We aimed to evaluate whether mothers of childhood brain cancer cases had greater potential residential exposure to Toxics Release Inventory (TRI) chemicals than control mothers during pregnancy. METHODS: We included 382 brain cancer cases diagnosed at < 10 years of age from 1993 through 1997 who were identified from four statewide cancer registries. One-to-one matched controls were selected by random-digit dialing. Computer-assisted telephone interviews were conducted. Using residential history of mothers during pregnancy, we measured proximity to TRI facilities and exposure index, including mass and chemicals released. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression to estimate brain cancer risk associated with TRI chemicals. RESULTS: Increased risk was observed for mothers living within 1 mi of a TRI facility (OR = 1.66 ; 95% CI, 1.11-2.48) and living within 1 mi of a facility releasing carcinogens (OR = 1.72 ; 95% CI, 1.05-2.82) for having children diagnosed with brain cancer before 5 years of age, compared to living > 1 mi from a facility. Taking into account the mass and toxicity of chemical releases, we found a nonsignificant increase in risk (OR = 1.25 ; 95% CI, 0.67-2.34) comparing those with the lowest versus highest exposure index. CONCLUSIONS: Risk of childhood brain cancers may be associated with living near a TRI facility ; however, this is an exploratory study and further studies are needed.     

Maternal exposure to occupational solvents and childhood leukemia

Many organic solvents are considered probable carcinogens. We carried out a population-based case-control study including 790 incident cases of childhood acute lymphoblastic leukemia and as many healthy controls, matched on age and sex. Maternal occupational exposure to solvents before and during pregnancy was estimated using the expert method, which involves chemists coding each individual's job for specific contaminants. Home exposure to solvents was also evaluated. The frequency of exposure to specific agents or mixtures was generally low. Results were generally similar for the period ranging from 2 years before pregnancy up to birth and for the pregnancy period alone. For the former period, the odds ratio (OR), adjusted for maternal age and sex, for any exposure to all solvents together was 1.11 [95% confidence interval (CI), 0.88-1.40]. Increased risks were observed for specific exposures, such as to 1,1,1-trichloroethane (OR = 7.55; 95% CI, 0.92-61.97), toluene (OR = 1.88; 95% CI, 1.01-3.47), and mineral spirits (OR = 1.82; 95% CI, 1.05-3.14). There were stronger indications of moderately increased risks associated with exposure to alkanes (C5-C17; OR = 1.78; 95% CI, 1.11-2.86) and mononuclear aromatic hydrocarbons (OR = 1.64; 95% CI, 1.12-2.41). Risk did not increase with increasing exposure, except for alkanes, where a significant trend (p = 0.04) was observed. Home exposure was not associated with increased risk. Using an elaborate exposure coding method, this study shows that maternal exposure to solvents in the workplace does not seem to play a major role in childhood leukemia.     

Occupation and lung cancer risk in the province of Trieste: a case-control study]

To investigate the relationship between occupation and lung cancer, a case-control study was performed in the province of Trieste, Italy, where metallurgical and mechanical industries, dock activities and shipbuilding and ship repairing are predominant. Through the local Cancer Registry, pathology records of 938 men who died of primary lung cancer (ICD 162) in a five-year period were examined. Residential, smoking and occupational histories were obtained from interviews of next of kin of 756 cases and 756 age-matched male controls (+/- 2 years). Occupational exposures to lung carcinogens were assessed according to a job-title based approach, identifying industries/occupations with well-recognized lung carcinogen exposures (list A) and industries/occupations with suspected lung carcinogen exposures (list B). Exposure to asbestos was classified as absent, possible or definite. After adjustment for cigarette smoking (four levels) and residence (three levels), a significant association was found between lung cancer and occupations in list A (RR = 2.28, 95% CI = 1.70-3.07) and in list B (RR = 1.33, 95% CI = 1.04-1.71). A significant excess risk was found for workers with definite exposure to asbestos when compared to those with no exposure to lung carcinogens (RR = 1.99, 95% CI = 1.43-2.76). A very high relative risk was observed among heavy smokers with definite exposure to asbestos (RR = 42.8). A stratified analysis showed that the combined effect of asbestos and smoking was compatible with that expected under a multiplicative model. The overall attributable risk in the population (ARp) for cigarette smoking was found to be 87.6%. The ARp fraction for occupations with well-established exposures to lung carcinogens (list A) was 16.2%. The ARp fraction increased to 25.5% (85% CI = 1.4-34.6) when occupations with suspected exposure to lung carcinogens (list B) were included. The ARp fraction for possible or definite exposure to asbestos was 20.1% (95% CI = 11.6-28.6).     

Parental occupational exposure to pesticides and the risk of childhood leukemia in Costa Rica

OBJECTIVES: Parental exposure to pesticides and the risk of leukemia in offspring were examined in a population-based case-control study in Costa Rica. METHODS: All cases of childhood leukemia (N=334), in 1995-2000, were identified at the Cancer Registry and the Children's Hospital. Population controls (N=579) were drawn from the National Birth Registry. Interviews of parents were conducted using conventional and icon-based calendar forms. An exposure model was constructed for 25 pesticides in five time periods. RESULTS: Mothers' exposures to any pesticides during the year before conception and during the first and second trimesters were associated with the risk [odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0-5.9; OR 22, 95% CI 2.8-171.5; OR 4.5, 95% CI 1.4-14.7, respectively] and during anytime (OR 2.2, 95% CI 1.0-4.8). An association was found for fathers' exposures to any pesticides during the second trimester (OR 1.5, 95% CI 1.0-2.3). An increased risk with respect to organophosphates was found for mothers during the first trimester (OR 3.5, 95% CI 1.0-12.2) and for fathers during the year before conception and the first trimester (OR 1.5, 95% CI 1.0-2.2 and OR 1.6, 95% CI 1.0-2.6, respectively), and benzimidazoles during the first, second, and third trimesters of pregnancy (OR 2.2, 95% CI 1.0-4.4; OR 2.2, 95% CI 1.0-5.0; OR 2.2, 95% CI 1.0-5.2, respectively). There was a suggestion of an exposure-response gradient for fathers as regards picloram, benomyl, and paraquat. Age at diagnosis was positively associated with fathers' exposures and inversely associated with mothers' exposures. CONCLUSIONS: The results suggest that parental exposure to certain pesticides may increase the risk of leukemia in offspring.     

Paternal occupational exposure to pesticides or herbicides as risk factors for cancer in children and young adults: a case-control study from the North of England

Researchers in numerous studies have suggested that preconception paternal occupational exposures to various substances, including pesticides and herbicides, may be involved in the etiology of childhood cancers. Using data from the Northern Region Young Persons' Malignant Disease Registry, the authors investigated whether paternal occupations likely to involve such exposures, as recorded at the time of a child's birth, were associated with children's cancer risk. The authors matched cases (n = 4,723), on sex and year of birth, to controls from 2 independent sources: (1) all other patients from the registry with a different cancer and (2) 100 cancer-free individuals per case from the Cumbrian Births Database. An inverse association existed, particularly in males, between lymphoid leukemia and paternal occupations with likely exposures to pesticides and/or herbicides. However, this was not significant after stratifying by residential status (urban versus rural). Results do not support a role for preconception paternal occupational exposures to pesticides or herbicides in the etiology of childhood cancer.     

Leukemia and non-Hodgkin's lymphoma in childhood and exposure to pesticides: results of a register-based case-control study in Germany

Previous studies have suggested an association between exposure to pesticides and different types of childhood cancer. This paper presents results from a population-based case-control interview study of parents of children less than 15 years of age, which was conducted in the states of West Germany from 1993 to 1997. Cases were 1,184 children with leukemia, 234 with non-Hodgkin's lymphoma, and 940 with a solid tumor; 2,588 controls were also included. Parental occupational exposures were found to be related to childhood cancer regardless of the time period of exposure and the type of cancer. This finding might partially be explained by different recall of past exposures by the parents of cases and controls. Residential use of insecticides was associated with childhood lymphoma: both extermination of insects by professional pest controllers (odds ratio (OR) = 2.6, 95% confidence interval (CI): 1.2, 5.7) and frequency of parental use of household insecticides (p for trend = 0.02) were significant risk factors for this diagnosis. The use of pesticides on farms was weakly related to childhood leukemia (OR = 1.5, 95% CI: 1.0, 2.2), while their use in gardens was not associated with childhood leukemia (OR = 1.0, 95% CI: 0.8, 1.2). The major strengths of this study were the population base and the large number of cases and controls included; a drawback was assessment of exposure on the basis of parental interviews. The data provide some evidence for an increased leukemia risk for children living on farms and for an association between use of household pesticides and risk of childhood leukemia or lymphoma.     

Acute lymphoblastic leukaemia among Spanish children and mothers'' occupation: a case-control study.

STUDY OBJECTIVE--The aim was to investigate the association between mothers' occupational exposure during pregnancy and the incidence of acute lymphoblastic leukaemia in children. DESIGN--The study was a case-control investigation. A face to face interview was used to assess exposures at work and relevant confounding variables. SETTING--The study was community based and was carried out in five provinces of Spain. SUBJECTS--128 cases less than 15 years of age were interviewed (91% of those eligible). Controls (one for each case) were chosen from the census lists and were matched on year of birth, sex and municipality. MEASUREMENTS AND MAIN RESULTS--Children of mothers working at home had a relative risk (RR) of 7.0 (95% CI = 1.59-30.79) of developing acute lymphoblastic leukaemia. Exposure to organic dust was associated with a RR of 5.5 (95% CI = 1.21-24.8). There was a statistically significant interaction between exposure to organic dust and working at home. The majority of women working at home were hired by local industries to sew different types of tissues (cotton, wool, synthetic fibres) on a machine. CONCLUSION--A similar association has not been reported before: if confirmed, this finding may suggest a new health concern.     

Maternal occupational exposure during pregnancy and the risk of spina bifida.

OBJECTIVES: A case-control study was carried out to explore associations between spina bifida and occupational exposure of the mother. METHODS: The cases were children with spina bifida aperta born between 1980 and 1992 from nine hospitals in the Netherlands. The controls were children born healthy in the same period as the cases, from hospitals and from the general population. Data collection was carried out in two steps. Firstly, postal questionnaires were sent to all the parents of cases and controls to gather information on occupations and potential confounders. In the second phase of the study, information on specific exposures was collected by means of job and task specific personal interviews. Interviews were performed with 55 case mothers and 66 control mothers who had occupations with a potential for chemical or physical exposure. Those exposures were assumed to be negligible for--for example, teachers and secretaries, so personal interviews were not indicated for these women. Information was collected on specific tasks in the period just after conception, and on the associated use of chemical or physical agents, frequency of exposure, and use of protective equipment. RESULTS: The analyses of occupation showed an increased risk for women working in agricultural occupations (OR = 3.4, CI:1.3-9.0), and, although less distinct, for cleaning women (OR = 1.7, CI:0.9-3.4). Only a few women seemed to be occupationally exposed to chemical or physical agents. No differences in occurrence of specific exposures could be detected between cases and controls. Besides, no differences were seen in pesticide or disinfectant exposure among case and control mothers in agricultural occupations. CONCLUSIONS: Occupational exposures of the mother during pregnancy were infrequent and did not seem to play an important part in the aetiology of spina bifida in this study. The association found between spina bifida and maternal agricultural occupations could not be explained by the use of pesticides by the mother or by any other occupational exposure.     

Reproductive outcome in offspring of parents occupationally exposed to lead in Norway

In Norway, great efforts have been made to protect both male and female employees against teratogenic exposures. Associations between occupational lead exposure and reproductive outcome in the offspring were studied. All births in Norway 1970–1993 with possible maternal or paternal occupational lead exposure were compared with a reference population of offspring of parents without occupational lead exposure. Offspring of lead exposed mothers had an increased risk of low birth weight (RR = 1.34; CI = 1.12–1.60) and neural tube defects (RR = 2.87; CI = 1.05–6.38). Effects on birth weight and gestational age showed significant dose-response associations. Offspring of lead exposed fathers had no increased risks of any of the analyzed reproductive outcomes. However, decreased risks were observed of low birth weight (RR = 0.91; CI = 0.86–0.96) and preterm birth (RR = 0.89; CI = 0.86–0.93). Further efforts seem to be needed to protect the offspring of lead-exposed mothers. Am. J. Ind. Med. 34:431–437, 1998. © 1998 Wiley-Liss, Inc.     

Leukemia in relation to occupational exposures to benzene and other agents: a case-control study nested in a cohort of gas and electric utility workers

BACKGROUND: Many occupational and environmental exposures have been implicated in the etiology of leukemia, but only a few, such as benzene, are well-established leukemogens. The risk of leukemia in a large cohort of gas and electricity utility workers with exposures to several suspected or confirmed carcinogens was investigated. METHODS: A case-control study nested within the cohort was conducted, with 72 leukemia cases identified among male workers, and 285 controls matched to the cases by year of birth. Only cases, and their matched controls, active in the company at the date of diagnosis were included. Exposure assessment was based on a job-exposure matrix (JEM) developed from expert judgment using a standardized procedure. RESULTS: The risk of leukemia was increased in workers with an estimated cumulative exposure to benzene > or = 16.8 ppm-years (OR = 3.6; 95% CI 1.1-11.7), and there was an indication of a dose-response relation (OR = 1.2; 95% CI 1.0-1.5 per 10 ppm-years increase in exposure). The link with benzene was more pronounced for acute leukemia than for chronic leukemia, but no association with a particular leukemia cell type was apparent. The risk of leukemia remained elevated for latency periods of 2, 5, or 10 years. CONCLUSIONS: From our evaluation, it could be estimated that the median TWA exposure to benzene among exposed workers was 0.16 ppm, i.e., within concentration ranges where an increased leukemia risk was usually not apparent in previous epidemiological studies. Although an increased leukemia risk may be real, it may also be related to other occupational factors not totally controlled for in the analysis, or to benzene exposures actually higher than expected.     

Breastfeeding,Other Early Life Exposures and Childhood Leukemia and Lymphoma

Childhood cancer incidence increases and although rare, it is a leading cause of mortality. Leukemia and lymphoma comprise 40% of all cancers in children but little is known of their etiology. In this study, we examined the associations of breastfeeding and other early life exposures with childhood leukemia and lymphoma. A population-based case–control study carried out in 2011–2013 comprised mothers of 190 incidents (2005–2013) of leukemia/lymphoma cases aged 1–19 yr at diagnosis and 384 population-based controls. Interviews based on a computerized structured questionnaire were conducted with the mothers. Multivariate logistic regression models adjusted for potential confounders assessed the association between breastfeeding patterns and childhood leukemia/lymphoma. Ever breastfeeding category was associated with a 64% decreased risk for childhood leukemia/lymphoma lsqb;odds ratio (OR) = 0.36, 95% confidence interval (CI): 0.22, 0.60lrqb; and similar trends, with a dose–response effect, were observed for any breastfeeding (exclusive and/or partial) category for 6, 12, and 18+ mo. Other infant exposures associated with cancer risk were child iron supplementation (OR = 0.39, 95% CI: 0.26, 0.59), pet ownership (OR = 0.50, 95% CI: 0.33, 0.78), paternal smoking (OR = 1.93, 95% CI: 1.18, 3.15), and having older siblings (OR = 1.18, 95% CI: 1.05, 1.33). Breastfeeding—a controllable and modifiable exposure—is inversely associated with risk for childhood leukemia and lymphoma with a dose–response effect.     

Ewing's bone sarcoma, paternal occupational exposure, and other factors.

To determine risk factors for Ewing's bone sarcoma, the authors interviewed mothers of 43 patients diagnosed between January 1978 and August 1986 and 193 controls in the San Francisco Bay Area, California, regarding medical and occupational history of parents and other factors related to the subjects and their immediate families. Controls were selected by using random digit dial telephone methods. Adjusted relative risk estimates suggest that risks were elevated for children whose fathers were engaged in agricultural occupations during the period from 6 months prior to conception of the subject up to the time of diagnosis for the patients or interview for the controls (relative risk (RR) = 8.8, 95% confidence interval (CI) 1.8-42.7) and for children whose fathers had occupational exposure to herbicides, pesticides, or fertilizers (RR = 6.1, 95% CI 1.7-21.9, p = 0.002). Prior ingestion of poison or an overdose of medication was more common in patients than in controls (RR = 4.4, 95% CI 1.4-13.5). These and other findings should be investigated in larger population-based studies to determine specific factors that may account for the associations.     

Childhood leukemia and infectious diseases in the first year of life: a register-based case-control study

In the Netherlands, a nationwide register of children with leukemia formed the basis for a case-control study (1973-1980). Population controls were matched with the cases for the year of birth, sex, and place of residence at the time of diagnosis. The information was collected by mailed questionnaires addressed to the parents. The analyses concerned infectious diseases in the first year of life of children with acute lymphocytic leukemia and their controls. Common colds, periods of fever, and primary childhood infections showed relative risks (RR) of 0.8, 0.9, and 0.8, respectively, after adjustment for birth order, family size, social class, and residential space. Furthermore, fewer cases reported infectious diseases which required hospitalization in their first year of life (RR = 0.6, 95% confidence interval (CI) = 0.4-1.0). The general infection risk profile of children with acute lymphocytic leukemia is compatible with these findings: there were more first-born children among the patients (RR = 1.8; 95% CI = 1.1-2.7), more children from one-child families (RR = 1.4; 95% CI = 0.8-2.3), more children of parents with higher education (RR = 1.2; 95% CI = 0.9-1.5), and more rooms in patient's houses (RR = 1.4; 95% CI = 0.6-2.6).     

中国职业性汞暴露对女工生殖功能影响的Meta分析

目的 综合分析职业性汞暴露对女工生殖功能的影响,筛选汞暴露的敏感生殖效应指标.方法 运用计算机和手工检索收集1989-2006年间国内发表的关于职业性汞暴露与女工生殖功能关系的文献,经严格筛选后,应用Rev Man软件对入选文献的研究结果进行一致性检验并采用相应的数学模型进行数据合并,采用Meta分析合并RR值作为各项目的 总效应指标.结果 纳入14篇文献(暴露组2148人,对照组2044人),与对照组比较,职业性汞暴露与女性月经经期(RR=1.82,95% CI:1.45～2.30)、月经周期(RR=2.03,95% CI:1.74～2.37)、月经量的改变(RR=2.06,95% CI:1.47～2.09)、痛经(RR=2.14,95% CI:1.54～2.99)、妊娠高血压(RR=2.17,95% CI:1.32～3.57)、死产死胎(RR=2.54,95% CI:1.41～4.56)及女工子代低体重出生(RR=3.39,95% CI:1.38～8.33)和出生缺陷(RR=2.67,95% CI:1.55～4.60)等的正相关有显著的统计学意义(P＜0.05).结论 职业性汞暴露可以引起女工月经经期、周期和经量改变,增加痛经,同时还会影响妊娠及其子代发育,表现为增加妊娠高血压和死产死胎的发生,并导致其子代低体重和发生出生缺陷.     

Temporal variation in the association between benzene and leukemia mortality

BACKGROUND: Benzene is a human carcinogen. Exposure to benzene occurs in occupational and environmental settings. OBJECTIVE: I evaluated variation in benzene-related leukemia with age at exposure and time since exposure. METHODS: I evaluated data from a cohort of 1,845 rubber hydrochloride workers. Benzene exposure-leukemia mortality trends were estimated by applying proportional hazards regression methods. Temporal variation in the impact of benzene on leukemia rates was assessed via exposure time windows and fitting of a multistage cancer model. RESULTS: The association between leukemia mortality and benzene exposures was of greatest magnitude in the 10 years immediately after exposure [relative rate (RR) at 10 ppm-years = 1.19; 95% confidence interval (CI), 1.10-1.29]; the association was of smaller magnitude in the period 10 to < 20 years after exposure (RR at 10 ppm-years = 1.05; 95% CI, 0.97-1.13); and there was no evidence of association > or = 20 years after exposure. Leukemia was more strongly associated with benzene exposures accrued at > or = 45 years of age (RR at 10 ppm-years = 1.11; 95% CI, 1.04-1.17) than with exposures accrued at younger ages (RR at 10 ppm-years = 1.01; 95% CI, 0.92-1.09). Jointly, these temporal effects can be efficiently modeled as a multistage process in which benzene exposure affects the penultimate stage in disease induction. CONCLUSIONS: Further attention should be given to evaluating the susceptibility of older workers to benzene-induced leukemia.     

Maternal occupational exposure to extremely low frequency magnetic fields during pregnancy and childhood leukemia

BACKGROUND: Pregnancy is a target period for events that could induce childhood leukemia. There has been little attention to possible effects of maternal occupational exposure to extremely low frequency magnetic fields (ELF-MF) during pregnancy. METHODS: We conducted a population-based, case-control study of 491 incident cases of acute lymphoblastic leukemia in children 0-9 years of age, matched on age and sex to 491 healthy controls. Cases were diagnosed in the Province of Québec between 1980 and 1993. Mothers were interviewed to obtain detailed prenatal occupational history; individual exposure to ELF-MF was estimated based on a method we recently developed. We used 3 metrics for analyzing exposure: cumulative, average and maximum levels. Analyses were carried out among all study women and among working women only. RESULTS: Comparing the highest 10% of exposed mothers to the others, the risk of leukemia among offspring was moderately increased by using any metric, in all women and among working women only. The highest odds ratio of 2.5 (95% confidence interval = 1.2-5.0) was found for maximum exposure attained in an occupation (>/=0.4 microtesla). CONCLUSIONS: Our results are compatible with an increased risk of childhood leukemia among children whose mothers were exposed to the highest occupational levels of ELF-MF during pregnancy.