Association of meteorological and geographical factors and risk of initial Pseudomonas aeruginosa acquisition in young children with cystic fibrosis.

Initial infection with the sentinel respiratory pathogen in children with cystic fibrosis (CF), Pseudomonas aeruginosa (Pa), is generally with environmental strains of this ubiquitous organism. The purpose of this study was to evaluate the associations between meteorological and geographical factors and risk of initial Pa acquisition in young children with CF. Using the U.S. Cystic Fibrosis Foundation Patient Registry from 2003 to 2009, 3463 patients met inclusion criteria, of which 48% (n = 1659) acquired Pa during follow-up. From multivariable Weibull regression, increased risk of Pa acquisition was associated with increasing temperature [hazard ratio (HR) per 1 °C: 1·13; 95% confidence interval (CI) 1·08-1·13], dew point (HR per 1 °C: 1·10, 95% CI 1·07-1·13), rainfall (HR per cm: 1·10, 95% CI 1·07-1·12), latitude (HR per 1 °C northing: 1·15, 95% CI 1·11-1·20), longitude (HR per 1 °C easting: 1·01, 95% CI 1·01-1·02) and elevation (HR per 100 m: 1·05, 95% CI 1·03-1·07). These results suggest that environmental factors may play a previously unrecognized role in the aetiology of initial Pa acquisition.

Pesticides, chemical and industrial exposures in relation to systemic lupus erythematosus.

Growing evidence suggests exposure to chemicals and industrial pollutants may increase risk of systemic lupus erythematosus (SLE). Here we review research on SLE associations with occupational and industrial exposures, primarily drawing on studies in human populations and summarizing epidemiologic research published in the past decade. The association of occupational silica exposure with SLE is well established, but key questions remain, including the required dose and susceptibility factors, and SLE risk due to other silicate exposures. Research on SLE and other exposures is less well developed, though several potential associations merit further consideration because of the consistency of preliminary human findings, experimental animal research, and biologic plausibility. These include pesticides and solvents, for which experimental findings also support investigation of specific agents, including organochlorines and trichloroethylene. Experimental findings and biologic plausibility suggest research on SLE and occupational exposure to hydrocarbons (i.e. mineral oils) is warranted, especially given the widespread exposures in the population. Experimental and limited human findings support further investigation of SLE related to mercury exposure, especially in dental occupations. Research on environmental risk factors in risk-enriched cohorts (family-based) is recommended, as is further investigation of exposures in relation to intermediate markers of effect (e.g. antinuclear antibodies), clinical features (e.g. nephritis), and outcomes.

Season is associated with Pseudomonas aeruginosa acquisition in young children with cystic fibrosis.

Pseudomonas aeruginosa, the principal respiratory pathogen in cystic fibrosis (CF) patients, is ubiquitous in the environment. Initial P. aeruginosa isolates in CF patients are generally environmental in nature. However, little information regarding seasonality of P. aeruginosa acquisition is available. We conducted a retrospective study to evaluate the seasonality of initial P. aeruginosa acquisition in young children with CF in the USA using the Cystic Fibrosis Foundation National Patient Registry from 2003 to 2009. Additionally, we assessed whether seasonal acquisition varied by climate zone. A total of 4123 children met inclusion criteria and 45% (n = 1866) acquired P. aeruginosa during a mean 2.0 years (SD 0.2 years) of follow up. Compared with winter, increased P. aeruginosa acquisition was observed in summer (incidence rate ratio (IRR): 1.22; 95% CI: 1.07-1.40) and autumn (IRR: 1.34; 95% CI: 1.18-1.52), with lower acquisition observed in spring (IRR: 0.81; 95% CI: 0.70-0.94). Seasonal variations in P. aeruginosa acquisition rates in the temperate and continental climate zones were similar to those in the overall cohort. In contrast, no significant seasonal effect was observed in the dry climate zone. In a corresponding analysis, no seasonal difference was observed in the rate of acquisition of Staphylococcus aureus, another common CF respiratory pathogen. These results provide preliminary support that climatic factors may be associated with initial P. aeruginosa acquisition in CF patients. Investigation and identification of specific risk factors, as well as awareness of seasonal variation, could potentially inform clinical recommendations including increased awareness of infection control and prevention strategies.

Determinants of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in house dust samples from four areas of the United States.

Determinants of levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) in dust in U.S. homes are not well characterized. We conducted a pilot study to evaluate the relationship between concentrations of PCDD/F in house dust and residential proximity to known sources, including industrial facilities and traffic. Samples from vacuum bag dust from homes of 40 residents of Detroit, Los Angeles, Seattle, or Iowa who participated in a population-based case-control study of non-Hodgkin lymphoma conducted in 1998-2000 were analyzed using high resolution gas chromatography/high resolution mass spectrometry for 7 PCDD and 10 PCDF congeners considered toxic by the U.S. Environmental Protection Agency (EPA). Locations of 10 types of PCDD/F-emitting facilities were obtained from the EPA; however only 4 types were located near study homes (non-hazardous waste cement kilns, coal-fired power plants, sewage sludge incinerators, and medical waste incinerators). Relationships between concentrations of each PCDD/F and proximity to industrial facilities, freight routes, and major roads were evaluated using separate multivariate regression models for each congener. The median (inter-quartile range [IQR]) toxic equivalence (TEQ) concentration of these congeners in the house dust was 20.3 pg/g (IQR=14.3, 32.7). Homes within 3 or 5 km of a cement kiln had 2 to 9-fold higher concentrations of 5 PCDD and 5 PCDF (p<0.1 in each model). Proximity to freight routes and major roads was associated with elevated concentrations of 1 PCDD and 8 PCDF. Higher concentrations of certain PCDD/F in homes near cement kilns, freight routes, and major roads suggest that these outdoor sources are contributing to indoor environmental exposures. Further study of the contribution of these sources and other facility types to total PCDD/F exposure in a larger number of homes is warranted.

Effects of radiation and lifestyle factors on risks of urothelial carcinoma in the Life Span Study of atomic bomb survivors.

Among the Life Span Study (LSS) of Atomic-bomb survivors, recent estimates showed that unspecified bladder cancer had high radiation sensitivity with a notably high female-to-male excess relative risk (ERR) per radiation dose ratio and were the only sites for which the ERR did not decrease with attained age. These findings, however, did not consider lifestyle factors, which could potentially confound or modify the risk estimates. This study estimated the radiation risks of the most prevalent subtype of urinary tract cancer, urothelial carcinoma, while accounting for smoking, consumption of fruit, vegetables, alcohol and level of education (a surrogate for socioeconomic status). Eligible study subjects included 105,402 (males = 42,890) LSS members who were cancer-free in 1958 and had estimated radiation doses. Members were censored due to loss of follow-up, incident cancer of another type, death, or the end of calendar year 2001. Surveys (by mail or clinical interview) gathered lifestyle data periodically for 1963-1991. There were 63,827 participants in one or more survey. Five hundred seventy-three incident urothelial carcinoma cases occurred, of which 364 occurred after lifestyle information was available. Analyses were performed using Poisson regression methods. The excess relative risk per weighted gray unit (the gamma component plus 10 times the neutron component, Gy(w)) was 1.00 (95% CI: 0.43-1.78) but the risks were not dependent upon age at exposure or attained age. Lifestyle factors other than smoking were not associated with urothelial carcinoma risk. Neither the magnitude of the radiation ERR estimate (1.00 compared to 0.96), nor the female-to-male (F:M) ERR/Gy(w) ratio (3.2 compared to 3.4) were greatly changed after accounting for all lifestyle factors. A multiplicative model of gender-specific radiation and smoking effects was the most revealing though there was no evidence of significant departures from either the additive or multiplicative joint effect models. Among the LSS cohort members with doses greater than 0.005 Gy(w) (average dose 0.21 Gy(w)), the attributable fraction of urothelial carcinoma due to radiation was 7.1% in males and 19.7% in females. Among current smokers, the attributable fraction of urothelial carcinoma due to smoking was 61% in males and 52% in females. Relative risk estimates of smoking risk were approximately two for smokers compared to nonsmokers. After adjustment for lifestyle factors, gender-specific radiation risks and the F:M ERR/Gy(w), the ratios of excess urothelial carcinoma risk were similar to the estimates without adjusting for lifestyle factors. Smoking was the primary factor responsible for excess urothelial carcinoma in this cohort. These findings led us to conclude that the radiation risk estimates of urothelial carcinoma do not appear to be strongly confounded or modified by smoking, consumption of alcohol, fruits, or vegetables, or level of education.

Residential proximity to industrial facilities and risk of non-Hodgkin lymphoma.

Industrial pollution has been suspected as a cause of non-Hodgkin lymphoma (NHL), based on associations with chemical exposures in occupational studies. We conducted a case-control study of NHL in four SEER regions of the United States, in which residential locations of 864 cases and 684 controls during the 10 years before recruitment were used to characterize proximity to industrial facilities reporting chemical releases to the Environmental Protection Agency's Toxics Release Inventory (TRI). For each of 15 types of industry (by 2-digit SIC code), we evaluated the risk of NHL associated with having lived within 2 miles of a facility, the distance to the nearest facility (miles categories of < or =0.5, >0.5-1.0, >1.0-2.0, >2 [referent]), and the duration of residence within 2miles (years categories of 10, 1-9, 0 [referent]), using logistic regression. Increased risk of NHL was observed in relation to lumber and wood products facilities (SIC 24) for the shortest distance of residential proximity (< or =0.5 mile: odds ratio [OR]=2.2, 95% confidence interval [CI]: 0.4-11.8) or the longest duration (10 years: OR=1.9, 95% CI: 0.8-4.8); the association with lumber facilities was more apparent for diffuse large B-cell lymphoma (lived within 2 miles: OR=1.7, 95% CI: 1.0-3.0) than for follicular lymphoma (OR=1.1, 95% CI: 0.5-2.2). We also observed elevated ORs for the chemical (SIC 28, 10 years: OR=1.5, 95% CI: 1.1-2.0), petroleum (SIC 29, 10 years: OR=1.9, 95% CI: 1.0-3.6), rubber/miscellaneous plastics products (SIC 30, < or =0.5mile: OR=2.7, 95% CI: 1.0-7.4), and primary metal (SIC 33, lived within 2miles: OR=1.3, 95% CI: 1.0-1.6) industries; however, patterns of risk were inconsistent between distance and duration metrics. This study does not provide strong evidence that living near manufacturing industries increases NHL risk. However, future studies designed to include greater numbers of persons living near specific types of industries, along with fate-transport modeling of chemical releases, would be informative.

Degreasing and risk of non-Hodgkin lymphoma.

OBJECTIVE: To investigate the relationship between selected solvent-related workplace tasks (degreasing, painting, gluing, stripping paint, staining) and risk of non-Hodgkin lymphoma (NHL). METHODS: We analysed occupational data from a large population-based case-control study of NHL conducted in the USA. For participants reporting occupations with possible exposure to organic solvents, job-specific interview modules were administered to elicit in-depth information on solvent-related workplace tasks and other exposure-related factors (225 cases, 189 controls). Unconditional logistic regression models were fit to calculate odds ratios (ORs) and 95% CI for average frequency, maximal frequency and cumulative number of hours having performed each task. Individuals with jobs rated as unexposed to organic solvents in the workplace (180 cases, 213 controls) were used as a reference group. RESULTS: We observed an increased risk of NHL among subjects in the highest category of maximal degreasing frequency (>520 h/year: OR 2.1, 95% CI 0.9 to 4.9, trend test p = 0.02). We found similar associations for the highest levels of average frequency and, among men, cumulative number of hours. Other solvent-related tasks were not associated with NHL. CONCLUSION: Findings from this case-control analysis of solvent-related tasks suggest that frequent degreasing work may be associated with an elevated risk of NHL.

Occupation/industry and risk of non-Hodgkin's lymphoma in the United States.

AIMS: To identify occupations and industries associated with non-Hodgkin's lymphoma (NHL) in a large population-based, case-control study in the USA. METHODS: Cases (n = 1189) of histologically confirmed malignant NHL ages 20-74 were prospectively identified in four geographic areas covered by the National Cancer Institute SEER Program. Controls (n = 982) were selected from the general population by random digit dialling (<65 years of age) and from residents listed in Medicare files (65-74 years of age). Odds ratios and 95% confidence intervals for occupations and industries were calculated by unconditional logistic regression analyses, adjusting for age, gender, ethnicity and study centre. Further analyses stratified for gender and histological subtype were also performed. RESULTS: Risk of NHL was increased for a few occupations and industries. Several white collar occupations, with no obvious hazardous exposures, had elevated risks, including purchasing agents and buyers, religious workers, physical therapists and information clerks. Occupations with excesses that may have exposures of interest include launderers and ironers, service occupations, food/beverage preparation supervisors, hand packers and packagers, roofing and siding, leather and leather products, transportation by air, nursing and personal care facilities, and specialty outpatient clinics. Significantly decreased risks of NHL were found for a number of occupations and industries including post-secondary teachers and chemical and allied products. CONCLUSIONS: The results of this study suggest that several occupations and industries may alter the risk of NHL. Our results support previously reported increased risks among farmers, printers, medical professionals, electronic workers and leather workers. These findings should be evaluated further in larger studies that have the power to focus on specific exposures and histological subtypes of NHL.

Dust and chemical exposures, and miscarriage risk among women textile workers in Shanghai, China.

INTRODUCTION: To investigate possible associations between miscarriage and occupational exposures in the Shanghai textile industry. METHODS: A retrospective cohort study of miscarriages among 1752 women in the Shanghai textile industry was conducted. Reproductive history was self-reported by women and occupational work histories were collected from factory personnel records. Occupational exposures were assigned by linking work history information to an industry-specific job-exposure matrix informed by factory-specific textile process information and industrial hygiene assessments. Estimates of cotton dust and endotoxin exposure were also assigned. Odds ratios (OR) and 95% CI were estimated by multivariate logistic regression, with adjustment for age at pregnancy, educational level, smoking status of the woman and her spouse, use of alcohol, and woman's year of birth. RESULTS: An elevation in risk of a spontaneously aborted first pregnancy was associated with exposure to synthetic fibres (OR 1.89, 95% CI 1.20 to 3.00) and mixed synthetic and natural fibres (OR 3.31, 95% CI 1.30 to 8.42). No increased risks were observed for women working with solvents, nor were significant associations observed with quantitative cotton dust or endotoxin exposures. Associations were robust and similar when all pregnancies in a woman's reproductive history were considered. CONCLUSIONS: Occupational exposure to synthetic fibres may cause miscarriages, and this possibility should be the subject of further investigation.

Systemic autoimmune disease mortality and occupational exposures.

OBJECTIVE: To generate hypotheses regarding occupational exposures that may cause systemic autoimmune diseases. METHODS: Based on examination of US death certificates, we identified deaths in 26 states for which a cause was listed as rheumatoid arthritis (RA) (n = 36,178), systemic lupus erythematosus (SLE) (n = 7,241), systemic sclerosis (n = 5,642), or other systemic autoimmune disease (n = 4,270). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to estimate associations between occupation and death from any systemic autoimmune disease, and from RA, SLE, and systemic sclerosis, specifically. Additionally, we estimated risks associated with occupational exposures, which were assigned using job-exposure matrices. RESULTS: A broad array of occupations was associated with death from systemic autoimmune diseases, including several of a priori interest. Farming occupation was associated with death from any systemic autoimmune disease (OR 1.3 [95% CI 1.2-1.4]), and increased risk was also seen with occupational exposure to animals and pesticides. Several industrial occupations were associated with death from any systemic autoimmune disease, including mining machine operators (OR 1.3 [95% CI 1.1-1.5]), miscellaneous textile machine operators (OR 1.2 [95% CI 1.0-1.4]), and hand painting, coating, and decorating occupations (OR 1.8 [95% CI 1.0-2.9]). These occupations were also significantly associated with death from the specific autoimmune diseases examined. Certain occupations entailing exposure to the public, such as teachers, were associated with systemic autoimmune disease-related death, whereas others, such as waiters and waitresses, were not. CONCLUSION: Our results suggest that death from systemic autoimmune diseases may be associated with occupational exposures encountered in farming and industry. The hypotheses generated in this study provide leads for future research on determinants of these diseases.

Cell markers, cytokines, and immune parameters in cement mason apprentices.

OBJECTIVE: Cement masons are known to have significant silica exposure, and silica exposure and silicosis are thought to increase risk of autoimmune disease. Because the mechanisms remain obscure, with inconclusive reports of systemic immune effects following silica exposure, our goal was to identify potential early markers of silica-related immunologic and respiratory effects. METHODS: We conducted a cross-sectional study of cement mason apprentices and electrician (control) apprentices. Demographics, dust exposure history, symptoms, spirometry, exhaled nitric oxide, and blood (for immunoglobulins, cytokines, cell counts, and surface markers) were obtained from 11 cement mason apprentices and a comparison group of 21 electrician apprentices. RESULTS: Masons had significantly higher (P < 0.05) masonry dust exposure (42 versus 9 dust-hour-years), serum interleukin-1beta (IL-1beta; 12 versus 9 pg/ml), IL-2 (20 versus 8 pg/ml), IL-4 (193 versus 67 pg/ml), IL-10 (44 versus 21 pg/ml), and interferon-gamma (139 versus 65 pg/ml) compared with electricians. In contrast, masons had significantly lower percentages of CD25+ (12% versus 20%) and CD69+ (4% versus 9%) lymphocytes. CONCLUSION: Mason apprentices had higher levels of serum proinflammatory cytokines and lower percentages of CD25+ and CD69+ lymphocytes than did electrician apprentices. These preliminary findings suggest that mason apprentices may be at greater risk of a systemic proinflammatory state that is potentially linked to immune dysregulation. Although distinct limitations of this preliminary data are recognized, this is consistent with early biologic effects leading to increased incidence of autoimmune disease among silica-exposed workers. Prospective studies are needed to validate these initial findings and clarify the temporal sequence of observed relationships.

Colorectal cancer incidence among female textile workers in Shanghai, China: a case-cohort analysis of occupational exposures.

Previous studies have suggested increased risks of colorectal cancers among textile industry workers, potentially related to synthetic fibers. To investigate risks of colon and rectum cancers in relation to these and other textile industry exposures, we conducted a case-cohort study nested within a cohort study of female employees from the Shanghai Textile Industry Bureau (STIB). Cox proportional hazard regression modeling was used to estimate hazard ratios (HR) for colon and rectum cancers associated with duration of employment (e.g., 0, >0 to <10, 10 to <20 years, > or =20 years) in various jobs classified according to process type and exposures to specific agents. Our findings indicate that certain long term exposures may pose increased risk of colorectal cancers, especially dyes and dye intermediates with colon cancer (> or =20 years exposure versus never, HR=3.9; 95% CI: 1.4-10.6), and maintenance occupation (HR = 2.3; 95% CI: 1.0-5.7) and metals exposure (HR = 2.0; 95% CI: 1.1-3.6) with rectum cancer. A decreased risk of rectum cancer was associated with exposure to natural fibers such as cotton (HR = 0.7; 95% CI: 0.5-0.9), and a trend of decreasing rectum cancer incidence was observed by category of cumulative quantitative cotton dust or endotoxin exposures, when exposures were lagged by 20 years.

Risk of lymphatic or haematopoietic cancer mortality with occupational exposure to animals or the public.

BACKGROUND: Occupational exposure to animals or the public could result in exposure to infectious agents, which may play a role in the aetiology of lymphohaematopoietic (LH) cancers. AIMS: To conduct a population based, case-control study of death certificate data from 1984 to 1998 in 24 US states in order to evaluate the risk of mortality from LH neoplasms associated with occupational exposure to animals or the public. METHODS: Cases were selected as those with an underlying cause of death of non-Hodgkin's lymphoma (NHL, n = 72,589), Hodgkin's disease (HD, n = 5479), multiple myeloma (n = 35,857), or leukaemia (n = 68,598); 912 615 controls were randomly selected from all remaining deaths, frequency matched on age, sex, race, and geographic region. RESULTS: Occupational exposure to animals was associated with modest increased risks of mortality from all four LH cancers; these associations varied by region. Occupational exposure to the public was associated with only negligible increased risk with LH cancer outcomes. Occupations involving animal exposure were predominantly agricultural, and the risks associated with employment in the livestock industry exceeded the corresponding risks associated with the crop industry for all outcomes except HD. CONCLUSIONS: Increased risks of NHL, HD, multiple myeloma, and leukaemia were associated with occupations that involved animal exposure. Regional differences in risk imply that the risks may be associated with exposure to specific livestock or farming practices. However, these associations may be confounded by other farming related exposures, such as pesticides. Because the use of death certificates to classify occupation may result in misclassification during aetiologically relevant time periods, these hypotheses should be further explored in studies with detailed information on lifetime occupation.

Integrative assessment of multiple pesticides as risk factors for non-Hodgkin's lymphoma among men.

BACKGROUND: An increased rate of non-Hodgkin's lymphoma (NHL) has been repeatedly observed among farmers, but identification of specific exposures that explain this observation has proven difficult. METHODS: During the 1980s, the National Cancer Institute conducted three case-control studies of NHL in the midwestern United States. These pooled data were used to examine pesticide exposures in farming as risk factors for NHL in men. The large sample size (n = 3417) allowed analysis of 47 pesticides simultaneously, controlling for potential confounding by other pesticides in the model, and adjusting the estimates based on a prespecified variance to make them more stable. RESULTS: Reported use of several individual pesticides was associated with increased NHL incidence, including organophosphate insecticides coumaphos, diazinon, and fonofos, insecticides chlordane, dieldrin, and copper acetoarsenite, and herbicides atrazine, glyphosate, and sodium chlorate. A subanalysis of these "potentially carcinogenic" pesticides suggested a positive trend of risk with exposure to increasing numbers. CONCLUSION: Consideration of multiple exposures is important in accurately estimating specific effects and in evaluating realistic exposure scenarios.

Occupation and the risk of adult glioma in the United States.

OBJECTIVE: Previous studies have observed increased glioma incidence associated with employment in the petroleum and electrical industries, and in farming. Several other occupations have also been associated with increased risk, but with inconsistent results. We evaluated associations between occupational title and glioma incidence in adults. METHODS: Cases were 489 patients with glioma diagnosed from 1994 to 1998 at three United States hospitals. Controls were 799 patients admitted to the same hospitals for non-malignant conditions. An experienced industrial hygienist grouped occupations that were expected to have similar tasks and exposures. The risk of adult glioma was evaluated for those subjects who ever worked in an occupational group for at least six months, those who worked longer than five years in the occupation, and those with more than ten years latency since starting work in the occupation. RESULTS: Several occupational groups were associated with increased glioma incidence for having ever worked in the occupation, including butchers and meat cutters (odds ratio [OR] = 2.4; 95% confidence limits [CL]: 1.0, 6.0), computer programmers and analysts (OR = 2.0; 95% CL: 1.0, 3.8), electricians (OR = 1.8; 95% CL: 0.8, 4.1), general farmers and farmworkers (OR = 2.5; 95% CL: 1.4, 4.7), inspectors, checkers, examiners, graders, and testers (OR = 1.5; 95% CL: 0.8, 2.7), investigators, examiners, adjustors, and appraisers (OR = 1.7; 95% CL: 0.8, 3.7), physicians and physician assistants (OR = 2.4; 95% CL: 0.8, 7.2), and store managers (OR = 1.6; 95% CL: 0.8, 3.1), whereas occupation as a childcare worker was associated with decreased glioma incidence (OR = 0.4; 95% CL: 0.2, 0.9). These associations generally persisted when the subjects worked longer than five years in the occupation, and for those with more than ten years latency since starting to work in the occupation. CONCLUSIONS: This is our first analysis of occupation and will guide future exposure-specific assessments.

Occupational exposure assessment in case-control studies: opportunities for improvement.

Community based case-control studies are an efficient means to study disease aetiologies, and may be the only practical means to investigate rare diseases. However, exposure assessment remains problematic. We review the literature on the validity and reliability of common case-control exposure assessment methods: occupational histories, job-exposure matrices (JEMs), self reported exposures, and expert assessments. Given the variable quality of current exposure assessment techniques, we suggest methods to improve assessments, including the incorporation of hygiene measurements: using data from administrative exposure databases; using results of studies identifying determinants of exposure to develop questionnaires; and where reasonable given latency and biological half life considerations, directly measuring exposures of study subjects.

Parental occupational exposures to electromagnetic fields and radiation and the incidence of neuroblastoma in offspring.

We examined parental occupational exposures to electromagnetic fields and radiation and the incidence of neuroblastoma in offspring. Cases were 538 children diagnosed with neuroblastoma between 1992 and 1994 in the United States or Canada. Age-matched controls were selected by random-digit dialing. Occupational exposures to electrical equipment and radiation sources were classified by an industrial hygienist, and average exposures to extremely low frequency magnetic fields were estimated using a job exposure matrix. Maternal exposure to a broad grouping of sources that produce radiofrequency radiation was associated with an increased incidence of neuroblastoma (odds ratio = 2.8; 95% confidence interval = 0.9-8.7). Paternal exposure to battery-powered forklifts was positively associated with neuroblastoma (odds ratio = 1.6; 95% confidence interval = 0.8-3.2), as were some types of equipment that emit radiofrequency radiation (odds ratios congruent with 2.0); however, the broad groupings of sources that produce ELF fields, radiofrequency radiation, or ionizing radiation were not associated with neuroblastoma. Paternal average extremely low frequency magnetic field exposure >0.4 microTesla was weakly associated with neuroblastoma (odds ratio = 1.6; 95% confidence interval = 0.9-2.8), whereas maternal exposure was not. Overall, there was scant supportive evidence of strong associations between parental exposures in electromagnetic spectrum and neuroblastoma in offspring.

Parental occupational exposures to chemicals and incidence of neuroblastoma in offspring.

To evaluate the effects of parental occupational chemical exposures on incidence of neuroblastoma in offspring, the authors conducted a multicenter case-control study, using detailed exposure information that allowed examination of specific chemicals. Cases were 538 children aged 19 years who were newly diagnosed with confirmed neuroblastoma in 1992-1994 and were registered at any of 139 participating hospitals in the United States and Canada. One age-matched control for each of 504 cases was selected through random digit dialing. Self-reported exposures were reviewed by an industrial hygienist, and improbable exposures were reclassified. Effect estimates were calculated using unconditional logistic regression, adjusting for child's age and maternal demographic factors. Maternal exposures to most chemicals were not associated with neuroblastoma. Paternal exposures to hydrocarbons such as diesel fuel (odds ratio (OR) = 1.5; 95% confidence interval (CI): 0.8, 2.6), lacquer thinner (OR = 3.5; 95% CI: 1.6, 7.8), and turpentine (OR = 10.4; 95% CI: 2.4, 44.8) were associated with an increased incidence of neuroblastoma, as were exposures to wood dust (OR = 1.5; 95% CI: 0.8, 2.8) and solders (OR = 2.6; 95% CI: 0.9, 7.1). The detailed exposure information available in this study has provided additional clues about the role of parental occupation as a risk factor for neuroblastoma.

An application of hierarchical regression in the investigation of multiple paternal occupational exposures and neuroblastoma in offspring.

BACKGROUND: We used hierarchical regression to study the effects of 46 paternal occupational exposures on the incidence of neuroblastoma in offspring. METHODS: The study population included 405 cases and 302 controls. The effect of each exposure was estimated using both conventional maximum likelihood and hierarchical regression. RESULTS: Using hierarchical regression, overall precision was greatly enhanced compared to the conventional analysis. In addition, adjustment of effect estimates based on prespecified prior distributions of the true effect parameters allowed a more consistent interpretation across the entire panel of exposures. Estimates for several metals and solvents were shrunk close to the null value, whereas estimates for several thinner solvents, diesel fuel, solders, wood dust, and grain dust remained moderately elevated. CONCLUSIONS: Hierarchical regression may mitigate some of the problems of the conventional approach by controlling for correlated exposures, enhancing the precision of estimates, and providing some adjustment of estimates based on prior knowledge.