Parental occupational exposures and risk of childhood cancer: a review

The spatial association between environmental pollution and long-term cancer mortality in Italy

Tumours are nowadays the second world‑leading cause of death after cardiovascular diseases. During the last decades of cancer research, lifestyle and random/genetic factors have been blamed for cancer mortality, with obesity, sedentary habits, alcoholism, and smoking contributing as supposed major causes. However, there is an emerging consensus that environmental pollution should be considered one of the main triggers. Unfortunately, all this preliminary scientific evidence has not always been followed by governments and institutions, which still fail to pursue research on cancer's environmental connections. In this unprecedented national-scale detailed study, we analyzed the links between cancer mortality, socio-economic factors, and sources of environmental pollution in Italy, both at wider regional and finer provincial scales, with an artificial intelligence approach. Overall, we found that cancer mortality does not have a random or spatial distribution and exceeds the national average mainly when environmental pollution is also higher, despite healthier lifestyle habits. Our machine learning analysis of 35 environmental sources of pollution showed that air quality ranks first for importance concerning the average cancer mortality rate, followed by sites to be reclaimed, urban areas, and motor vehicle density. Moreover, other environmental sources of pollution proved to be relevant for the mortality of some specific cancer types. Given these alarming results, we call for a rearrangement of the priority of cancer research and care that sees the reduction and prevention of environmental contamination as a priority action to put in place in the tough struggle against cancer.

Why We Will Continue to Lose Our Battle with Cancers If We Do Not Stop Their Triggers from Environmental Pollution

Besides our current health concerns due to COVID-19, cancer is a longer-lasting and even more dramatic pandemic that affects almost a third of the human population worldwide. Most of the emphasis on its causes has been posed on genetic predisposition, chance, and wrong lifestyles (mainly, obesity and smoking). Moreover, our medical weapons against cancers have not improved too much during the last century, although research is in progress. Once diagnosed with a malignant tumour, we still rely on surgery, radiotherapy, and chemotherapy. The main problem is that we have focused on fighting a difficult battle instead of preventing it by controlling its triggers. Quite the opposite, our knowledge of the links between environmental pollution and cancer has surged from the 1980s. Carcinogens in water, air, and soil have continued to accumulate disproportionally and grow in number and dose, bringing us to today's carnage. Here, a synthesis and critical review of the state of the knowledge of the links between cancer and environmental pollution in the three environmental compartments is provided, research gaps are briefly discussed, and some future directions are indicated. New evidence suggests that it is relevant to take into account not only the dose but also the time when we are exposed to carcinogens. The review ends by stressing that more dedication should be put into studying the environmental causes of cancers to prevent and avoid curing them, that the precautionary approach towards environmental pollutants must be much more reactionary, and that there is an urgent need to leave behind the outdated petrochemical-based industry and goods production.

Parental occupational exposures and the risk of childhood sporadic retinoblastoma: a report from the Children's Oncology Group

OBJECTIVES

We examined associations between parental occupational chemical exposures up to 10 years before conception and the risk of sporadic retinoblastoma among offspring.

METHODS

In our multicentre study on non-familial retinoblastoma, parents of 187 unilateral and 95 bilateral cases and 155 friend controls were interviewed by telephone. Exposure information was collected retroactively through a detailed occupational questionnaire that asked fathers to report every job held in the 10 years before conception, and mothers 1 month before and during the index pregnancy. An industrial hygienist reviewed all occupational data and assigned an overall exposure score to each job indicating the presence of nine hazardous agents.

RESULTS

We estimated elevated ORs for unilateral and bilateral retinoblastoma among offspring of fathers who were exposed to polycyclic aromatic hydrocarbons or paints in the 10 years before conception. However, only for exposure to paints did confidence limits exclude the null for bilateral disease (OR: 8.76, 95% CI: 1.32 to 58.09). Maternal prenatal exposure to at least one of the nine agents was related to increased risk of unilateral disease in their children (OR: 5.25, 95% CI: 1.14 to 24.16). Fathers exposed to at least one of the nine agents and who were ≥30 years of age were at increased risk of having a child diagnosed with bilateral retinoblastoma (OR: 6.59, 95% CI: 1.34 to 32.42).

CONCLUSIONS

Our results suggest a role for several hazardous occupational exposures in the development of childhood retinoblastoma.

Molecular epidemiology of acute leukemia in children: causal model, interaction of three factors-susceptibility, environmental exposure and vulnerability period

Acute leukemias have a huge morphological, cytogenetic and molecular heterogeneity and genetic polymorphisms associated with susceptibility. Every leukemia presents causal factors associated with the development of the disease. Particularly, when three factors are present, they result in the development of acute leukemia. These phenomena are susceptibility, environmental exposure and a period that, for this model, has been called the period of vulnerability. This framework shows how the concepts of molecular epidemiology have established a reference from which it is more feasible to identify the environmental factors associated with the development of leukemia in children. Subsequently, the arguments show that only susceptible children are likely to develop leukemia once exposed to an environmental factor. For additional exposure, if the child is not susceptible to leukemia, the disease does not develop. In addition, this exposure should occur during a time window when hematopoietic cells and their environment are more vulnerable to such interaction, causing the development of leukemia. This model seeks to predict the time when the leukemia develops and attempts to give a context in which the causality of childhood leukemia should be studied. This information can influence and reduce the risk of a child developing leukemia.

Parental, In Utero, and Early-Life Exposure to Benzene and the Risk of Childhood Leukemia: A Meta-Analysis

Benzene is an established cause of adult leukemia, but whether it is associated with childhood leukemia remains unclear. We conducted a meta-analysis in which we reviewed the epidemiologic literature on this topic and explored causal inference, bias, and heterogeneity. The exposure metrics that we evaluated included occupational and household use of benzenes and solvents, traffic density, and traffic-related air pollution. For studies of occupational and household product exposure published from 1987 to 2014, the summary relative risk for childhood leukemia was 1.96 (95% confidence interval (CI): 1.53, 2.52; n = 20). In these studies, the summary relative risk was higher for acute myeloid leukemia (summary relative risk (sRR) = 2.34, 95% CI: 1.72, 3.18; n = 6) than for acute lymphoblastic leukemia (sRR = 1.57; 95% CI: 1.21, 2.05; n = 14). The summary relative risk was higher for maternal versus paternal exposure, in studies that assessed benzene versus all solvents, and in studies of gestational exposure. In studies of traffic density or traffic-related air pollution published from 1999 to 2014, the summary relative risk was 1.48 (95% CI: 1.10, 1.99; n = 12); it was higher for acute myeloid leukemia (sRR = 2.07; 95% CI: 1.34, 3.20) than for acute lymphoblastic leukemia (sRR = 1.49; 95% CI: 1.07, 2.08) and in studies that involved detailed models of traffic pollution (sRR = 1.70; 95% CI: 1.16, 2.49). Overall, we identified evidence of associations between childhood leukemia and several different potential metrics of benzene exposure.

A case-control study of paternal occupational exposures and the risk of childhood sporadic bilateral retinoblastoma

BACKGROUND

The risk factors for sporadic (ie, non-familial) retinoblastoma remain largely unknown.

OBJECTIVES

We examined the relationship between paternal occupational exposures from jobs held 10 years and 1 year prior to conception and the risk of sporadic bilateral retinoblastoma in children.

METHODS

Paternal occupational data were obtained for 198 incident cases diagnosed with sporadic bilateral retinoblastoma from January 1998 to May 2006 and 245 referral-based controls from the case child's relatives and friends who were matched to 135 of the cases on birth year. Industrial hygienists independently assigned exposure scores for nine agents. Adjusted ORs and 95% CIs were computed using logistic regression models, using the full sample of cases and controls as well as subset of cases with matched controls only.

RESULTS

There was some indication of an elevated risk associated with paternal pesticide exposure in the 10 years prior to conception (OR=1.64; 95% CI 1.08 to 2.50) as well as in the year before conception (OR=2.12; 95% CI 1.25 to 3.61). However, results for pesticide exposure were inconsistent and varied by analysis approach. An increased risk was also observed for non-welding metal exposure during the 10 years prior to conception in the full (OR=1.35; 95% CI 0.86 to 2.12) and matched (OR=1.40; 95% CI 0.82 to 2.37) samples, but not in the year before conception. Exposure-response trends were observed for pesticides and non-welding metal exposures.

CONCLUSIONS

Our findings suggest a potential role of paternal occupational exposures to non-welding metals and perhaps pesticides in the aetiology of childhood retinoblastoma.

The role of employers and supervisors in promoting pesticide safety behavior among Florida farmworkers

BACKGROUND

Farmworkers in Florida's nursery and fernery industries have an elevated risk of exposure to chemical pesticides due to the enclosed nature of their workplaces and their close contact with pesticide-treated plant material. Farmworkers' beliefs about chemical exposures and their perception of employer's or supervisor's valuing of safety may limit the practice of workplace hygiene.

METHODS

Three hundred eighty-two surveys from workers in the nursery and fernery industries in North Central Florida were collected as part of the Together for Agricultural Safety (TAS) Project from 1999-2001. Univariate analyses and multivariate Ordinary Least Squares regression are used to examine the role of individual and structural characteristics on handwashing practices.

RESULTS

Workplace practices such as the provision of written notices of recent pesticide application and the provision of convenient handwashing facilities are important predictors of workplace hygiene. Although farmworker attitudes and beliefs towards the utility of such practices and potential hazards are associated with behavior, they are less significant than the structural variables.

CONCLUSIONS

In order for farmworkers to engage in safety behavior that will protect their health, they must be adequately instructed and supported by employers and/or supervisors.

Father's occupational exposure to carcinogenic agents and childhood acute leukemia: a new method to assess exposure (a case-control study)

Background

Medical research has not been able to establish whether a father's occupational exposures are associated with the development of acute leukemia (AL) in their offspring. The studies conducted have weaknesses that have generated a misclassification of such exposure. Occupations and exposures to substances associated with childhood cancer are not very frequently encountered in the general population; thus, the reported risks are both inconsistent and inaccurate. In this study, to assess exposure we used a new method, an exposure index, which took into consideration the industrial branch, specific position, use of protective equipment, substances at work, degree of contact with such substances, and time of exposure. This index allowed us to obtain a grade, which permitted the identification of individuals according to their level of exposure to known or potentially carcinogenic agents that are not necessarily specifically identified as risk factors for leukemia. The aim of this study was to determine the association between a father's occupational exposure to carcinogenic agents and the presence of AL in their offspring.

Methods

From 1999 to 2000, a case-control study was performed with 193 children who reside in Mexico City and had been diagnosed with AL. The initial sample-size calculation was 150 children per group, assessed with an expected odds ratio (OR) of three and a minimum exposure frequency of 15.8%. These children were matched by age, sex, and institution with 193 pediatric surgical patients at secondary-care hospitals. A questionnaire was used to determine each child's background and the characteristics of the father's occupation(s). In order to determine the level of exposure to carcinogenic agents, a previously validated exposure index (occupational exposure index, OEI) was used. The consistency and validity of the index were assessed by a questionnaire comparison, the sensory recognition of the work area, and an expert's opinion.

Results

The adjusted ORs and 95% confidence intervals (CI) were 1.69 (0.98, 2.92) during the preconception period; 1.98 (1.13, 3.45) during the index pregnancy; 2.11 (1.17, 3.78) during breastfeeding period; 2.17 (1.28, 3.66) after birth; and 2.06 (1.24, 3.42) for global exposure.

Conclusion

This is the first study in which an OEI was used to assess a father's occupational exposure to carcinogenic agents as a risk factor for the development of childhood AL in his offspring. From our results, we conclude that children whose fathers have been exposed to a high level of carcinogenic agents seem to have a greater risk of developing acute leukemia. However, confounding factors cannot be disregarded due to an incomplete control for confounding.

Lifestyle-related factors and environmental agents causing cancer: an overview

The increasing incidence of a variety of cancers after the Second World War confronts scientists with the question of their origin. In Western countries, expansion and ageing of the population as well as progress in cancer detection using new diagnostic and screening tests cannot fully account for the observed growing incidence of cancer. Our hypothesis is that environmental factors play a more important role in cancer genesis than it is usually agreed. (1) Over the last 2-3 decades, alcohol consumption and tobacco smoking in men have significantly decreased in Western Europe and North America. (2) Obesity is increasing in many countries, but the growing incidence of cancer also concerns cancers not related to obesity nor to other known lifestyle-related factors. (3) There is evidence that the environment has changed over the time period preceding the recent rise in cancer incidence, and that this change, still continuing, included the accumulation of many new carcinogenic factors in the environment. (4) Genetic susceptibility to cancer due to genetic polymorphism cannot have changed over one generation and actually favours the role of exogenous factors through gene-environment interactions. (5) Age is not the unique factor to be considered since the rising incidence of cancers is seen across all age categories, including children, and adolescents. (6) The fetus is specifically vulnerable to exogenous factors. A fetal exposure during a critical time window may explain why current epidemiological studies may still be negative in adults. We therefore propose that the involuntary exposure to many carcinogens in the environment, including microorganisms (viruses, bacteria and parasites), radiations (radioactivity, UV and pulsed electromagnetic fields) and many xenochemicals, may account for the recent growing incidence of cancer and therefore that the risk attributable to environmental carcinogen may be far higher than it is usually agreed. Of major concern are: outdoor air pollution by carbon particles associated with polycyclic aromatic hydrocarbons; indoor air pollution by environmental tobacco smoke, formaldehyde and volatile organic compounds such as benzene and 1,3 butadiene, which may particularly affect children and food contamination by food additives and by carcinogenic contaminants such as nitrates, pesticides, dioxins and other organochlorines. In addition, carcinogenic metals and metalloids, pharmaceutical medicines and some ingredients and contaminants in cosmetics may be involved. Although the risk fraction attributable to environmental factors is still unknown, this long list of carcinogenic and especially mutagenic factors supports our working hypothesis according to which numerous cancers may in fact be caused by the recent modification of our environment.

The multitude and diversity of environmental carcinogens

We have recently proposed that lifestyle-related factors, screening and aging cannot fully account for the present overall growing incidence of cancer. In order to propose the concept that in addition to lifestyle related factors, exogenous environmental factors may play a more important role in carcinogenesis than it is expected, and may therefore account for the growing incidence of cancer, we overview herein environmental factors, rated as certainly or potentially carcinogenic by the International Agency for Research on Cancer (IARC). We thus analyze the carcinogenic effect of microorganisms (including viruses), radiations (including radioactivity, UV and pulsed electromagnetic fields) and xenochemicals. Chemicals related to environmental pollution appear to be of critical importance, since they can induce occupational cancers as well as other cancers. Of major concerns are: outdoor air pollution by carbon particles associated with polycyclic aromatic hydrocarbons; indoor air pollution by environmental tobacco smoke, formaldehyde and volatile organic compounds such as benzene and 1,3 butadiene, which may particularly affect children, and food pollution by food additives and by carcinogenic contaminants such as nitrates, pesticides, dioxins and other organochlorines. In addition, carcinogenic metals and metalloids, pharmaceutical medicines and cosmetics may be involved. Although the risk fraction attributable to environmental factors is still unknown, this long list of carcinogenic and especially mutagenic factors supports our working hypothesis according to which numerous cancers may in fact be caused by the recent modification of our environment.

Orthopaedic metals and their potential toxicity in the arthroplasty patient

The long-term effects of metal-on-metal arthroplasty are currently under scrutiny because of the potential biological effects of metal wear debris. This review summarises data describing the release, dissemination, uptake, biological activity, and potential toxicity of metal wear debris released from alloys currently used in modern orthopaedics. The introduction of risk assessment for the evaluation of metal alloys and their use in arthroplasty patients is discussed and this should include potential harmful effects on immunity, reproduction, the kidney, developmental toxicity, the nervous system and carcinogenesis.

Parental Occupational Exposure and the Risk of Acute Lymphoblastic Leukemia in Offspring in Israel

OBJECTIVE

Parental employment in occupations that have potential exposures to organic solvents or pesticides could be associated with the risk of childhood acute lymphoblastic leukemia (ALL) in their offspring.

METHODS

We explored this hypothesis by studying the association with respect to exposure time windows. Our case-control study included 224 children, 112 diagnosed with ALL and 112 matched controls.

RESULTS

A significantly higher odds ratio (OR) was found between childhood ALL and reported parental occupational exposures. Analysis of exposures of both parents by exposure time windows revealed significant OR during the preconception and postnatal periods separately.

CONCLUSIONS

The results provide support to the association between parental occupational exposures and ALL in their children. These results should be interpreted cautiously because of the small numbers, biases characterizing case-control studies, and the use of hospital-based controls.

Factores de riesgo para los tumores óseos malignos pediátricos

INTRODUCTION

Cancer is the result of the interaction of two kinds of determinants: genetic (endogenous) and environmental (exogenous). In the last few decades, pediatric oncology as a whole has progressed, including knowledge of malignant osseous tumors (MOT). Although advances have been made in diagnostic and therapeutic aspects, little progress has taken place in our knowledge of the risk factors involved in their etiopathogenesis.

OBJECTIVE

This review has three objectives: a) to provide an update on MOT-related risk factors in the child and adult population; b) to disseminate knowledge of the main MOT-related risk factors among our colleagues in order to promote research into these factors, diagnosis and future prevention, and c) to request help from our colleagues in the Environment and Pediatric Cancer research project.

MATERIAL AND METHODS

We performed a systematic review of the literature published in the last 30 years on risk factors implicated in the etiopathogenesis of MOT, using Medline, Cancerlit, Science Citation Index and Embase. The search profiles used were: pediatric/childhood malignant bone tumors, pediatric/ childhood bone cancer/neoplasm, osteosarcoma/bone sarcoma/Ewing's sarcoma and risk factors/etiology/epidemiology. The most interesting articles were selected and the most relevant references contained therein were retrieved.

RESULTS

MOT represent 6-7 % of all pediatric neoplasms. The most frequent types are osteosarcoma (OS) and Ewing's sarcoma (ES), representing 56 % and 34 % respectively. OS-related risk factors are the following: a) previous osseous disease (Paget's disease); b) familial-genetic factors (hereditary retinoblastoma, Li-Fraumeni syndrome, Rothmund-Thompson syndrome, Bloom syndrome, familial OS, Diamond-Blackfan anemia); c) chemical factors (antineoplastic drugs); d) physical factors (ionizing radiation); e) biologic factors; f) parental occupation, and g) other factors (artificial osseous implants and traumatisms). ES-related risk factors are the following: a) ethnic-cultural (Caucasian race); b) genetic factors; c) parental occupation (herbicide, pesticide and fertilizer exposure); d) maternal obstetric history, and e) other factors (parental smoking and inguinal hernia).

CONCLUSIONS

Most causes of MOT are unknown. Based on different levels of scientific evidence, the main factors implicated in the etiopathogenesis of OS are: Paget's disease, hereditary retinoblastoma, Li-Fraumeni syndrome, antineoplastic drugs, and ionizing radiation. The main factors related to ES are: Caucasian race, parental occupation, parental smoking, and surgery for inguinal hernia. The main obstacles to greater knowledge of MOT-related factors are: a) their multiple origin; b) the low prevalence in the population; c) lack of environmental health training in pediatrics, and d) the low public and private investment in this research field.

Diesel exhaust particles cause increased levels of DNA deletions after transplacental exposure in mice

Diesel exhaust particles (DEP) are a major source of air-borne pollution and are linked to increased risk of disease including lung cancer. Here we investigated effects of exposure to DEP on the frequency of DNA deletions, levels of oxidative DNA damage and DNA adduct formation during embryonic development in mice. Pregnant dams were orally exposed to various doses of DEP (500, 250, 125, 62.5, 31.25 mg/kg/day) at embryonic days 10.5-15.5. We determined the frequency of 70 kb DNA deletions spanning exons 6-18 at the p(un) allele that results in black-pigmented spots in the unpigmented retinal pigment epithelium in the eyes of p(un)/p(un) offspring mice. DEP caused a significant increase in the frequency of DNA deletions. Levels of 8-OH deoxyguanosine indicating oxidative DNA damage were within the limits of the unexposed mouse embryos. 33P post-labeling analysis revealed very low levels of DNA adducts in the embryo tissue. Thus, transplacental exposure to DEP resulted in a significant increase in the frequency of DNA deletions in the mouse fetus and such genetic alterations in the offspring may have pathological consequences later in life.

Maternal effects and cancer risk in the progeny of mice exposed to X-rays before conception

To investigate in an animal model whether preconceptual X-ray exposure leads to an altered tumor rate and spectrum in the offspring, a transgeneration carcinogenesis study was carried out. Female mice received X-ray irradiation (2 x 2 Gray) 2 weeks prior to mating with untreated males. After weaning, half of the descendants were exposed for 6 months to the immunomodulating and tumor-promoting compound cyclosporine A (CsA) by diet, the others remained untreated. The animals were maintained for their entire lifespan, terminal sacrifices were carried out after 28 months. Complete autopsy was performed, and three protocol organs (lung, liver and spleen) were examined histologically, together with any suspicious lesions in other organs. Fertility and the lifetime of the maternal mice were reduced by the X-ray irradiation, and their incidence of lung and liver tumors was increased as compared to non-irradiated mice. The descendants of all groups revealed comparable body weights and mortality rates. The incidence of hematopoietic/lymphoreticular tissue tumors increased in the female hybrids by 6 months of CsA-treatment. A higher incidence of lung and liver tumors in the sham-treated male progeny of irradiated mothers was detected, pointing to a possible germ cell-transmitted alteration initiated by the preconceptual maternal X-ray exposure.

Mouse models for induced genetic instability at endogenous loci

Exposure to environmental factors and genetic predisposition of an individual may lead individually or in combination to various genetic diseases including cancer. These diseases may be a consequence of genetic instability resulting in large-scale genomic rearrangements, such as DNA deletions, duplications, and translocations. This review focuses on mouse assays detecting genetic instability at endogenous loci. The frequency of DNA deletions by homologous recombination at the pink-eyed unstable (p(un)) locus is elevated in mice with mutations in ATM, Trp53, Gadd45, and WRN genes and after exposure to carcinogens. Other quantitative in vivo assays detecting loss of heterozygosity events, such as the mammalian spot assay, Dlb-1 mouse and Aprt mouse assays, are also reviewed. These in vivo test systems may predict hazardous effects of an environmental agent and/or genetic predisposition to cancer.

Traffic density and the risk of childhood leukemia in a Los Angeles case-control study

PURPOSE

To investigate the relationship between traffic density and the risk of childhood leukemia.

METHODS

The study group consisted of 212 cases and 202 controls from the London et al. (1991) study of childhood leukemia conducted in the Los Angeles area during 1978 to 1984. Using GIS methods, traffic counts on all streets within 1500 feet of each subject's residence of longest duration were determined. From these counts, an integrated distance-weighted traffic density measure was calculated for each subject for use as the analytic variable. Additional information, including magnetic fields and wire-code, was obtained from the original case-control study. Association between traffic density and leukemia, and confounding and effect modification by other variables, were assessed using standard matched case-control analyses.

RESULTS

Although the unadjusted traffic density-childhood leukemia rate ratios were slightly elevated, this weak association was explained by confounding by wire code. Wire code remained associated with leukemia after controlling for traffic density. There was little evidence of effect modification between traffic density and magnetic fields, wire code or other variables.

CONCLUSIONS

There is no evidence of an association of traffic density with childhood leukemia in the Los Angeles case-control study.

Persistent Genomic Instability in the YeastSaccharomyces cerevisiaeInduced by Ionizing Radiation and DNA-Damaging Agents

A "hypermutable" genome is a common characteristic of cancer cells, and it may contribute to the progressive accumulation of mutations required for the development of cancer. It has been reported that mammalian cells surviving exposure to gamma radiation display several highly persistent genomic instability phenotypes which may reflect a hypermutability similar to that seen in cancer. These phenotypes include an increased mutation frequency and a decreased plating efficiency, and they continue to be observed many generations after the radiation exposure. The underlying causes of this genomic instability have not been fully determined. We show here that exposure to gamma radiation and other DNA-damaging treatments induces a similar genomic instability in the yeast Saccharomyces cerevisiae. A dose-dependent increase in intrachromosomal recombination was observed in cultures derived from cells surviving gamma irradiation as many as 50 generations after the exposure. Increased forward mutation frequencies and low colony-forming efficiencies were also observed. Persistently elevated recombination frequencies in haploid cells were dominant after these cells were mated to nonirradiated partners, and the elevated recombination phenotype was also observed after treatment with the DNA-damaging agents ultraviolet light, hydrogen peroxide, and ethyl methanesulfonate. Radiation-induced genomic instability in yeast may represent a convenient model for the hypermutability observed in cancer cells.

Pesticide exposure of children in an agricultural community: evidence of household proximity to farmland and take home exposure pathways

Children's exposure to organophosphorus (OP) pesticides in an agricultural community in central Washington State was determined. Spot urine and hand wipe samples were collected from 109 children 9 months to 6 years of age, as were house dust samples, and wipe samples from various surfaces. Children were categorized based on parental occupation (agricultural vs nonagricultural) and on household proximity to pesticide-treated orchards. Median house dust concentrations of dimethyl OP pesticides in homes of agricultural families were seven times higher than those of reference families (1. 92 vs 0.27 microg/g; P<0.001). Median pesticide metabolite concentrations in agricultural children were five times higher than those in reference children (0.05 vs 0.01 microg/ml; P=0.09). Median pesticide concentrations in housedust (P=0.01) and metabolite concentrations in urine (P=0.01) from agricultural families were significantly higher in the children living near treated orchards (within 200 ft or 60 m) than those living more distant. Ten of 61 agricultural children had detectable OP pesticide levles on their hands, whereas none of the reference children had detectable levels. These findings indicate that children living with parents who work with agricultural pesticides, or who live in proximity to pesticide-treated farmland, have higher exposures than do other children living in the same community

Childhood cancer in the offspring of male sawmill workers occupationally exposed to chlorophenate fungicides

The objective of this study was to determine whether paternal occupational exposure to chlorophenol fungicides and their dioxin contaminants is associated with childhood cancer in the offspring of sawmill workers. We used data from 23,829 British Columbian sawmill workers employed for at least 1 continuous year between 1950 and 1985 in 11 sawmills that used chlorophenates. Probabilistic linkage of the sawmill worker cohort to the provincial marriage and birth files produced an offspring cohort of 19,674 children born at least 1 year after the initiation of employment in the period 1952-1988. We then linked the offspring cohort to the British Columbia Cancer Registry. We included all malignancies in cases younger than 20 years of age that appeared on the cancer registry between 1969 and 1993. We calculated standardized incidence ratios (SIRs) using the British Columbia population as a reference. A nested case-control analysis assessed the effects of paternal cumulative exposure and windows of exposure on the risk of developing cancer in the offspring. We identified 40 cases of cancer during 259,919 person-years of follow-up. The all-cancer SIR was 1.0 [95% confidence interval (CI), 0.7-1.4]; the SIR for leukemia was 1.0 (CI, 0.5-1.8); and the SIR for brain cancer was 1.3 (CI, 0.6-2.5). The nested case-control analysis showed slightly increased risks in the highest categories of chlorophenol exposure, although none was statistically significant. Our analyses provide little evidence to support a relationship between the risk of childhood cancer and paternal occupational exposure to chlorophenate fungicides in British Columbian sawmills.

Effect of ionizing radiation on transgenerational appearance of p(un) reversions in mice

Multiple genetic changes are required for the development of a malignant tumor cell and many environmentally induced cancers show a delayed onset of > 20 years following exposure. In fact, the frequency of genetic changes in cancer cells is higher than can be explained by random mutation. A high level of genetic instability in a subpopulation of cells may be caused by a mutator phenotype transmitted through many cell divisions. We have determined the effects of irradiation of parental male mice on the frequency and characteristics of mitotically occurring DNA deletion events at the p(un) locus in the offspring. Reversion of the p(un) marker in mouse embryos is due to deletion of 70 kb of DNA resulting in fur spots in the offspring. We found that irradiation of male mice caused a significantly higher frequency of large spots in the offspring, indicative of the induction of DNA deletions early in embryo development. These deletion events occurred, however, many cell divisions after irradiation. The present data indicate that exposure of the germline to ionizing radiation results in induction of delayed DNA deletions in offspring mice.

Reduced fertility among female wood workers exposed to formaldehyde

BACKGROUND

The aim of the study was to investigate whether exposure to formaldehyde, organic solvents or other chemicals in the wood-processing industry affects the fertility of women.

METHODS

For this purpose, a retrospective study on time to pregnancy was conducted among female wood workers who had given birth during 1985-1995. Data on pregnancy history, time to pregnancy, occupational exposures, and potential confounders were collected by a questionnaire; 64% (699/1,094) participated. The exposure assessment was conducted by an occupational hygienist. The data on time to pregnancy were analyzed with the discrete proportional hazards regression.

RESULTS

Exposure to formaldehyde was significantly associated with delayed conception: adjusted fecundability density ratio, FDR, was 0.64 (95% CI 0.43-0.92). At high exposure if no gloves were used, the FDR was 0.51 (% CI 0.28-0.92). Exposure to phenols, dusts, wood dusts, or organic solvents was not related to the time to pregnancy. Additionally, an association was observed between exposure to formaldehyde and an increased risk of spontaneous abortion (concerning previous spontaneous abortions, reported by the women). Associations between exposure to formaldehyde or to organic solvents and endometriosis, and between exposure to organic solvents or to dusts and salpingo-oophoritis were also suggested.

CONCLUSIONS

The study suggests that a woman's occupational exposure to formaldehyde has an adverse effect on fertility.

Cancer incidence and risks in selected agricultural settlements in the Negev of Israel

Medical staff of two Negev kibbutzim invited epidemiologists to help them investigate cancer rates among their members. Our objectives were (a) to determine whether the cancer rate in the kibbutzim was elevated or abnormal and (b) to determine the role of agricultural and other relevant exposures if cancer incidence was elevated. We validated cases of cancer by kibbutz records and by surveying other information; we computed expected values on the basis of the age-sex-calendar period and site-specific cancer incidence rates reported by the Israel Cancer Registry for the entire population; and we compared the data for the 2 kibbutzim with data derived for similar age and sex groups in 2 other kibbutzim, which were assumed not to have increased cancer rates. In addition, we planned and conducted a case-referent study, including the design, pretest, and use of questionnaires, including data about lifetime exposures (i.e., type of work and its duration, agricultural and industrial chemicals, smoking and alcohol use, demographic variables, health experiences, and family history). In only one of the kibbutzim, for which high cancer rates were suspected, was there significant excess for all sites in persons who were less than 40 y of age. In one of the "comparison" kibbutzim, we found increased cancer rates overall. Much of the excess in the high cancer kibbutzim was in hematological cancer (i.e., leukemia and lymphoma). Multiple years of work in fields, orchards, and landscape, as well as orchard work that commenced before 1960, were associated with increased risk of cancer (p < .08). We also found an association between cancer rate and numbers of industrial chemicals used (p < .08). Pipe and cigarette smoking were also associated with increased cancer incidence. In the multivariate analysis, the association with calendar year in which orchard work was started and multiple exposures to industrial chemicals was stronger than associations noted in the univariate analyses. Although duration of agricultural work or multiple industrial exposures were clearly associated with increase in cancer risk, we were unable to identify the causal role of specific agent(s). Nonetheless, educational programs for cancer prevention can be based, in part, on the results of such a study.

Paternal exposures: impact on reproductive and developmental outcome. An overview

Experimental and epidemiologic investigations document the adverse consequences of an array of paternal exposures on the development of subsequent offspring. Male-mediated abnormalities have been reported after exposure to therapeutic and recreational drugs, to chemicals in the workplace and environment and to ionizing radiation. The impact on progeny outcome includes: an increase in congenital malformations, spontaneous abortions, fetal resorptions; low birth weight; increase in childhood cancers; developmental, neurobehavioral, neuroendocrine, neurochemical abnormalities; effects in F2 generation progeny. Fertility is often unaffected. The comparative influence of genetic, epigenetic and nongenetic mechanisms in the etiology of paternally-mediated adverse outcomes is unknown. There is no a priori reason to assume that male-mediated effects are limited to the agents studied to date. The broad spectrum of alterations recorded after exposure to a variety of unrelated agents suggests the need for a more focused effort and multidisciplinary exploration of the potential impact of the male parent on reproductive outcome.

Childhood leukaemia and exposure to pesticides: results of a case-control study in northern Germany

The association between childhood leukaemia and exposure to pesticides was examined in a population-based case-control study conducted in Lower Saxony, Northern Germany. Between July 1988 and June 1992, 219 newly diagnosed cases were identified, of whom 173 participated in the study. Two sex- and age-matched control groups were recruited: local controls from the same communities as the newly diagnosed cases of leukaemia and state controls from other randomly selected communities in Lower Saxony. An additional study group consisted of 175 cases of solid tumours. When the leukaemia cases were compared with the local controls, positive associations with parental occupational exposure, particularly agriculture-related exposure, were observed, which were statistically non-significant. A significant association was found for pesticide use in gardens (odds ratio = 2.52, 95% confidence interval: 1.0-6.1). No positive associations were seen when the leukaemia cases were compared to the state controls, but this finding could be explained by a higher proportion of state controls living in rural areas. In communities with a significantly elevated standardised incidence ratio of childhood leukaemia over the last decade (1984-1993), the prevalence of pesticide use in the garden was 21%, compared with the 10% in other communities. None of the examined risk factors were more common among cases of solid tumours. Our findings add some evidence to the hypothesis that pesticides are a risk factor for childhood leukaemia, and there are good reasons to consider abundant pesticide use in rural areas as a possible cause for clustering of childhood leukaemia.

Trichloroethylene--a review of the literature from a health effects perspective

This report reviews the literature on the impact of exposure to trichloroethylene (TCE) on human health. Special emphasis is given to the health effects reported in excess of national norms by participants in the TCE Subregistry of the Volatile Organic Compounds Registry of the National Exposure Registries--persons with documented exposure to TCE through drinking and use of contaminated water. The health effects reported in excess by some or all of the sex and age groups studied were speech and hearing impairments, effects of stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease, urinary tract disorders, and skin rashes.

Incidence and risk factors for childhood brain tumors in the Ile de France

A case-control study investigating risk factors for childhood brain tumors was conducted in the Ile de France (Paris region). During a 2-year period (1985-1987) 109 newly diagnosed cases were identified and, of these, 75 could be interviewed. In the same region, 113 population controls, frequency-matched for year of birth, were interviewed. Odds ratios adjusted for child's age and sex and for maternal age were estimated for each risk factor present in utero or during childhood by conditional logistic regression. Statistically significant associations were found for the following risk factors: farm residence, cat scratches, home treated with pesticides, passive smoking, family history of cancer, antihistamine intake. Intake of vitamin supplements during childhood was associated with a decrease in risk. This study is part of a multicentric case-control study coordinated by the International Agency for Research on Cancer and its results will be compared for consistency, and pooled with those of other centers using the same protocol.

Risk factors for Wilms tumor. Report from the National Wilms Tumor Study

BACKGROUND

Previous epidemiologic studies have indicated that several factors may be associated with an increased risk of Wilms tumor including paternal occupational exposures, maternal exposure during pregnancy to cigarettes, coffee or tea, oral contraceptives, hormonal pregnancy tests, hair-coloring products, maternal hypertension, vaginal infection during pregnancy, and higher birth weight of the child. The current study examines the nonoccupational risk factors using questionnaire data from a large national collaborative clinical trial.

METHODS

Parents of 200 children registered with the National Wilms Tumor Study and 233 matched controls, identified using telephone random-digit dialing, completed a self-administered questionnaire about a variety of risk factors.

RESULTS

As opposed to some previous studies, no association was found for mother's smoking during pregnancy (10+ cigarettes per day; odds ratio [OR] = 0.73; 95% confidence interval [CI] = 0.40-1.34), maternal consumption of coffee or tea during pregnancy (4+ cups per day; OR = 1.31; CI = 0.57-3.01), or hypertension during pregnancy (OR = 0.96; CI = 0.45-2.06). In addition, no association was found in this study for hormone exposure during pregnancy, hair dye use, vaginal infection during pregnancy, or high birth weight. A previously unreported association with a history of household insect extermination was found (OR = 2.16; CI = 1.24-3.75).

CONCLUSIONS

In general, the study failed to confirm most of the previously reported maternal risk factors for Wilms tumor. Understanding the possible role of paternal exposures may be the best objective for further research on potential risk factors for Wilms tumor.

Evaluation of the national cancer program and proposed reforms

A statement by some 68 prominent national experts in industrial medicine, carcinogenesis, epidemiology, and public health, released at a February 4, 1992 press conference in Washington, D.C., charged that the National Cancer Institute (NCI) has confused the public by repeated claims of winning the war against cancer. In fact, age standardized incidence rates have increased sharply over recent decades, while ability to treat and cure most cancers has not materially improved. Furthermore, the NCI has minimized evidence for increasing cancer rates which are largely attributed to smoking and to diet. In so doing, NCI trivializes the importance of occupational carcinogens as non-smoking-attributable causes of lung and other cancers, and ignores the tenuous and inconsistent evidence for the causal role of diet per se and also the important role of carcinogenic dietary contaminants. Reflecting this near exclusionary blame-the-victim theory of cancer causation, with support from the American Cancer Society and industry, the NCI discounts the role of avoidable involuntary exposures to industrial carcinogens in air, water, food, the home, and the workplace. The NCI has also failed to provide scientific guidance to Congress and regulatory agencies on fundamental principles of carcinogenesis and epidemiology, and on the critical need to reduce avoidable exposures to environmental and occupational carcinogens. Contrary to NCI, analysis of their $2 billion budget reveals very limited allocations for research on primary cancer prevention, and for occupational cancer which receives only $19 million annually, 1% of NCI's total budget. Problems of professional mindsets in NCI leadership--fixation on diagnosis, treatment, and basic research (much of questionable relevance) and the neglect of cancer prevention--are exemplified by the composition of the Executive President's Cancer Panel and the National Cancer Advisory Board. Contrary to the explicit mandate of the National Cancer Act, the Board is virtually devoid of recognized authorities in occupational and environmental carcinogenesis. These problems are further compounded by institutionalized conflicts of interest reflected in the composition of past Cancer Panels, and of the current Board of Overseers of the Memorial Sloan Kettering Cancer Center, NCI's prototype comprehensive cancer center, with their closely interlocking financial interests with the cancer drug and other industries. Comprehensive reforms of NCI policies and priorities are overdue. Implementation of such reforms is, however, unlikely in the absence of further support from industrial medicine professionals, which is here solicited, besides action by Congress and concerned citizen groups.

Case-control study of leukaemia and non-Hodgkin's lymphoma among children aged 0-4 years living in west Berkshire and north Hampshire health districts

OBJECTIVE

To investigate the relation between parental employment in the nuclear industry and childhood leukaemia and non-Hodgkin's lymphoma.

DESIGN

Case-control study. SETTING-West Berkshire and Basingstoke and North Hampshire District Health Authorities.

SUBJECTS

54 children aged 0-4 years who had leukaemia or non-Hodgkin's lymphoma diagnosed during 1972-89, who were born in the study area and were resident there when cancer was diagnosed. Six controls were selected for each case: four from hospital delivery registers and two from livebirth registers maintained by the NHS central register. Controls were matched for sex, date of birth (within six months), and area of residence at birth and time of diagnosis.

MAIN OUTCOME MEASURES

Parents' employment by the nuclear industry and exposure to ionising radiation at work.

RESULTS

Five (9%) of the 54 cases and 14 (4%) of the 324 controls had fathers or mothers, or both, who had been employed by the nuclear industry (relative risk 2.2, 95% confidence interval 0.6 to 6.9). Nuclear industry employees who work in areas where exposure to radiation is possible are given film badges to monitor their exposure to external penetrating ionising radiation. Three fathers of cases and two fathers of controls (and no mothers of either) had been monitored in this way before their child was conceived (relative risk 9.0, 95% confidence interval 1.0 to 107.8). No father (of a case or control) had accumulated a recorded dose of more than 5 mSv before his child was conceived, and no father had been monitored at any time in the four years before his child was conceived. A dose-response relation was not evident among fathers who had been monitored.

CONCLUSIONS

These results suggest that the children of fathers who had been monitored for exposure to external penetrating ionising radiation in the nuclear industry may be at increased risk of developing leukaemia before their fifth birthday. The finding is based on small numbers and could be due to chance. If the relationship is real the mechanisms are far from clear, except that the effect is unlikely to be due to external radiation; the possibility that it could be due to internal contamination by radioactive substances or some other exposure at work should be pursued. The above average rates of leukaemia in the study area cannot be accounted for by these findings.

Epidemiology of Wilms tumor

Wilms tumor affects approximately one child per 10,000 worldwide before the age of 15 years. Incidence rates appear to be slightly elevated for U.S. and African Blacks in comparison to Whites, but are only half as great among Asians. Several case-control studies have suggested that paternal occupational or maternal hormonal exposures during pregnancy may increase the risk of Wilms tumor, but small numbers of subjects and inconsistencies in the patterns of exposures do not permit firm conclusions to be drawn. It is unlikely that such environmental exposures play a major role in the etiology of Wilms tumor. The median age-at-onset of Wilms tumor is 38 months in the U.S. National Wilms Tumor Study series, with cases in girls occurring on average 6 months later than in boys. Patients with bilateral tumors, aniridia, cryptorchism/hypospadias, Beck-with-Wiedemann syndrome, or intralobar nephrogenic rests tend to be diagnosed much younger than average (median 17-27 months). Those with familial disease or multicentric tumors have intermediate age-at-onset distributions, while those with perilobar nephrogenic rests are diagnosed at older ages. The epidemiologic features suggest that somatic mosaicism, rather than a germline mutation, may be responsible for some of the bilateral and multicentric cases.

Evaluation of the national cancer program and proposed reforms

A statement by 68 prominent national experts in cancer prevention, carcinogenesis, epidemiology, and public health, released at a February 4, 1992, press conference in Washington, D.C., charged that the National Cancer Institute (NCI) has misled and confused the public by repeated claims of winning the war against cancer. In fact, age-standardized incidence rates have escalated to epidemic proportions over recent decades, while the ability to treat and cure most cancers has not materially improved. Furthermore, the NCI has minimized evidence for increasing cancer rates, which are largely attributed to smoking, trivializing the importance of occupational carcinogens as non-smoking attributable causes of lung and other cancers, and to diet per se, in spite of tenuous and inconsistent evidence and ignoring the important role of carcinogenic dietary contaminants. Reflecting this near exclusionary blame-the-victim theory of cancer causation, with lockstep support from the American Cancer Society and industry, the NCI discounts the role of avoidable involuntary exposures to industrial carcinogens in air, water, food, the home, and the workplace. The NCI has also failed to provide any scientific guidance to Congress and regulatory agencies on fundament principles of carcinogenesis and epidemiology, and on the critical needs to reduce avoidable exposures to environmental and occupational carcinogens. Analysis of the +2 billion NCI budget, in spite of fiscal and semantic manipulation, reveals minimal allocations for research on primary cancer prevention, and for occupational cancer, which receives only +19 million annually, 1 percent of NCI's total budget. Problems of professional mindsets in the NCI leadership, fixation on diagnosis, treatment, and basic research, much of questionable relevance, and the neglect of cancer prevention, are exemplified by the composition of the National Cancer Advisory Board. Contrary to the explicit mandate of the National Cancer Act, the Board is devoid of members authoritative in occupational and environmental carcinogenesis. These problems are further compounded by institutionalized conflicts of interest reflected in the composition of past executive President's Cancer Panels, and of the current Board of Overseers of the Sloan-Kettering Memorial Cancer Center, the NCI's prototype comprehensive cancer center, with their closely interlocking financial interests with the cancer drug and other industries. Drastic reforms of NCI policies and priorities are long overdue. Implementation of such reforms is, however, unlikely in the absence of further support from industrial medicine professionals, besides action by Congress and concerned citizen groups.

International variations in the incidence of neuroblastoma

The International Agency for Research on Cancer has coordinated a worldwide study of childhood cancer incidence, with data from over 50 countries. We present here the results for neuroblastoma. In predominantly white Caucasian populations the age-standardized rate was 7-12 per million, and 6-10% of all childhood cancers were neuroblastomas. Rates were highest in the first year of life (25-50 per million, 30% of total neuroblastoma incidence), and decreased with age to 15-20 per million (50% of the total) at age 1-4, 2-4 per million (15%) at 5-9 and 1-1.5 per million (5%) at 10-14. In the United States, black children had an incidence of 8.5 per million compared with 11.5 among Whites; Blacks tended to be older than Whites at diagnosis. The highest rate in Africa was in Bulawayo, Zimbabwe (8.0 per million) and the lowest in West Nile, Uganda, with no cases registered. Incidence in Israel was similar to that in many white populations, with Jews having a particularly high rate. In other parts of West Asia neuroblastoma had a low relative frequency, suggesting that incidence is low. Rates were also low throughout much of southern and eastern Asia, including India and China. Incidence in Japan was somewhat higher, though less than in Western countries, with the deficit most pronounced in the first year of life; these data relate to the period before mass screening of infants for neuroblastoma in the regions concerned. Incidence was generally higher in regions and among ethnic groups enjoying a higher standard of living, though previous studies within single countries had suggested that neuroblastoma is more common among less affluent groups. Blacks in Africa and the United States may have a weaker genetic predisposition to neuroblastoma, but some of the deficit in many developing countries is likely to be due to under-diagnosis.

Male-mediated teratogenesis and other reproductive effects: biologic and epidemiologic findings and a plea for clinical research

This paper reviews biologic and epidemiologic evidence that prefertilization and perifertilization exposures to fathers influence a variety of reproductive outcomes, including fertilization, miscarriage, low birth weight, congenital anomalies, cancer, and neurodevelopmental and other childhood health problems. Males and females bring an equal number of chromosomes to their progeny, but their genomes may affect different aspects of reproduction. While the key male role principally ends at fertilization, there is growing experimental and human evidence that factors relating both to prefertilization and perifertilization exposure also play a role post fertilization. Some negative human epidemiologic findings reflect the fact that routinely gathered information usually generates detailed descriptions of maternal exposures and does not collect records regarding prefertilization paternal exposures. The absence of extensive human evidence should be interpreted as a deficiency in research rather than an absence of male-mediated adverse reproductive outcomes. More than 60 different compounds or industrial processes have been identified as increasing defects in human sperm and possibly increasing the risk to offspring from male-mediated exposures. Further research needs to include better characterizations of both maternal and paternal prefertilization and perifertilization exposures, in order to assess more accurately their relative effects. Pediatricians confronted with adverse pregnancy and antenatal health outcomes should obtain detailed information on relevant prefertilization exposures of both parents.

Use of a job-exposure matrix to evaluate parental occupation and childhood cancer

We examined the association between parental occupation and childhood cancer among 252 incident cases of childhood cancer (ages 0-14, diagnosed 1976-83) and 222 controls selected by random digit dialing in Denver, Colorado (USA). A job-exposure matrix was used to assign parental exposures based on job titles, emphasizing chemicals that were implicated in previous studies. All cancers, acute lymphocytic leukemia (ALL), and brain cancer were examined in relation to parental occupation during the year prior to the birth of the child. Elevated odds ratios (OR), all with confidence intervals extending below the null, were found for maternal exposure to benzene (OR = 1.9), petroleum/coke pitch/tar (OR = 2.2), and soot (OR = 3.3) in relation to total cancers. The ORs for total cancer and paternal exposure to all hydrocarbons combined was 1.0. Results for individual hydrocarbons and ALL showed larger odds ratios, including aniline (OR = 2.1), benzene (OR = 1.6), and petroleum/coke pitch/tar (OR = 1.6). Potential exposure to creosote was strongly associated with brain cancer (OR = 3.7) based on five exposed cases (95 percent confidence interval = 0.8-16.6). Control for other potential childhood cancer risk factors did not alter the results substantially. In spite of uncertainties due to small numbers and errors in exposure classification, results tend to corroborate past research that suggests an association between specific parental occupational exposures and childhood cancer.