Parental occupational exposures to chemicals and incidence of neuroblastoma in offspring

Trends in childhood cancer incidence: review of environmental linkages

Cancer in children is rare and accounts for about 1% of all malignancies. In the developed world, however, it is the commonest cause of disease-related deaths in childhood, carrying with it a great economic and emotional cost. Cancers are assumed to be multivariate, multifactorial diseases that occur when a complex and prolonged process involving genetic and environmental factors interact in a multistage sequence. This article explores the available evidence for this process, primarily from the environmental linkages perspective but including some evidence of the genetic factors.

Environmental hazards: evidence for effects on child health

The human fetus, child, and adult may experience adverse health outcomes from parental or childhood exposures to environmental toxicants. The fetus and infant are especially vulnerable to toxicants that disrupt developmental processes during relatively narrow time windows. This review summarizes knowledge of associations between child health and development outcomes and environmental exposures, including lead, methylmercury, polychlorinated biphenyls (PCBs), dioxins and related polyhalogenated aromatic hydrocarbons (PHAHs), certain pesticides, environmental tobacco smoke (ETS), aeroallergens, ambient air toxicants (especially particulate matter [PM] and ozone), chlorination disinfection by-products (DBPs), sunlight, power-frequency magnetic fields, radiofrequency (RF) radiation, residential proximity to hazardous waste disposal sites, and solvents. The adverse health effects linked to such exposures include fetal death, birth defects, being small for gestational age (SGA), preterm birth, clinically overt cognitive, neurologic, and behavioral abnormalities, subtle neuropsychologic deficits, childhood cancer, asthma, other respiratory diseases, and acute poisoning. Some environmental toxicants, notably lead, ionizing radiation, ETS, and certain ambient air toxicants, produce adverse health effects at relatively low exposure levels during fetal or child developmental time windows. For the many associations supported by limited or inadequate epidemiologic evidence, major sources of uncertainty include the limited number of studies conducted on specific exposure-outcome relationships and methodologic limitations. The latter include (1) crude exposure indices, (2) limited range of exposure levels, (3) small sample sizes, and (4) limited knowledge and control of potential confounders. Important knowledge gaps include the role of preconceptual paternal exposures, a topic much less studied than maternal or childhood exposures. Large longitudinal studies beginning before or during early pregnancy are urgently needed to accurately measure and assess the relative importance of parental and childhood exposures and evaluate relatively subtle health outcomes such as neuropsychologic and other functional deficits. Large case-control studies are also needed to assess the role of environmental exposures and their interactions with genetic factors in relatively uncommon outcomes such as specific types of birth defects and childhood cancers. There is also an urgent need to accelerate development and use of biomarkers of exposure and genetic susceptibility in epidemiologic studies. This review supports the priority assigned by international agencies to relationships between child health and air quality (indoor and outdoor), lead, pesticides, water contaminants, and ETS. To adequately address such priorities, governments and agencies must strengthen environmental health research capacities and adopt policies to reduce parental and childhood exposures to proven and emerging environmental threats.

Paint thinner exposure inhibits testosterone synthesis and secretion in a reversible manner in the rat

Occupational exposure and sniffing of toluene-based organic solvents is an important public health problem. In this study, we have investigated the effects of paint thinner inhalation on testosterone synthesis and secretion in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into three groups and exposed to paint thinner in a glassy cage for 15 and 30 days (2 h/day). A group of rats was allowed to recover for 15 days after 30 days of exposure. Toluene concentration (the largest constituent in thinner, 66%) was set at 1500 ppm in the inhaled air. At the end, all animals were decapitated and blood samples obtained. Testes and seminal vesicles were removed and weighed out. Serum total testosterone levels were determined by chemiluminescence enzyme immunoassay. Testicular tissue specimens were processed for semi-quantitative evaluation of immunohistochemical testosterone staining and light microscopy. Intensity of immunostaining was evaluated on a scale between 0 (no staining), 1 (minimal), 2 (mild), 3 (moderate) and 4 (strong staining). Serum testosterone levels (ng/ml) were decreased by 15-day (3.31+/-0.61) and 30-day (1.17+/-0.54, p<0.02) thinner exposure compared to the controls (3.91+/-1.03). Another group of rats exposed to thinner for 30 days and then allowed to recover for a period of 15 days had significantly elevated levels of testosterone values (3.77+/-1.1; p<0.05). Immunohistochemical testosterone staining of the cytoplasm of Leydig cells was moderate (3+) and mild (2+) in 15 and 30 days thinner inhalation groups, respectively. Strong staining (4+) was restored following the recovery period. Testicular weight was significantly reduced in all test groups compared to the control values (p<0.01). Diameters of seminiferous tubules were significantly decreased in the solvent exposed groups with enlarged connective tissue. The present findings suggest that paint thinner inhalation inhibits testosterone synthesis and secretion by a direct action on the Leydig cells in a reversible manner.

Trichloroethylene cancer epidemiology: a consideration of select issues

A large body of epidemiologic evidence exists for exploring causal associations between cancer and trichloroethylene (TCE) exposure. The U.S. Environmental Protection Agency 2001 draft TCE health risk assessment concluded that epidemiologic studies, on the whole, support associations between TCE exposure and excess risk of kidney cancer, liver cancer, and lymphomas, and, to a lesser extent, cervical cancer and prostate cancer. As part of a mini-monograph on key issues in the health risk assessment of TCE, this article reviews recently published scientific literature examining cancer and TCE exposure and identifies four issues that are key to interpreting the larger body of epidemiologic evidence: a) relative sensitivity of cancer incidence and mortality data ; b) different classifications of lymphomas, including non-Hodgkin lymphoma ; c) differences in data and methods for assigning TCE exposure status ; and d) different methods employed for causal inferences, including statistical or meta-analysis approaches. The recent epidemiologic studies substantially expand the epidemiologic database, with seven new studies available on kidney cancer and somewhat fewer studies available that examine possible associations at other sites. Overall, recently published studies appear to provide further support for the kidney, liver, and lymphatic systems as targets of TCE toxicity, suggesting, as do previous studies, modestly elevated (typically 1.5-2.0) site-specific relative risks, given exposure conditions in these studies. However, a number of challenging issues need to be considered before drawing causal conclusions about TCE exposure and cancer from these data.

Factores de riesgo asociados a los tumores neonatales. Experiencia de una unidad de salud medioambiental pediátrica (PEHSU-Valencia)

BACKGROUND

Neonatal tumors (NT) result from a variable combination of constitutional and environmental determinants. Multiple risk factors (RF) are involved in their development, although most are unknown.

OBJECTIVE

To document the constitutional, environmental, preconceptional and transplacental RF associated with the development of NT with greater or lesser scientific evidence.

PATIENTS AND METHODS

We investigated known RF in NT diagnosed at La Fe University Children's Hospital from January 1990 to December 1999, using a questionnaire completed by parents in a personal interview, either at the Pediatric Environmental Health Specialty Unit (PEHSU-Valencia) or at their home. RF associated with NT and childhood cancer were identified through a literature review of the last 25 years through Medline, Cancerlit, Science Citation Index, and Embase.

RESULTS

The questionnaire was completed in 59 of 74 NT diagnosed during the period studied. All patients were Caucasians born in Spain. Constitutional-genetic factors were identified in 13.6 %: dominant hereditary syndromes in 5 (familial retinoblastoma in 1 and tuberous sclerosis in 4), and non-hereditary chromosomal syndromes in 3 (trisomy 21). Notable environmental factors were: a) ionizing radiation: preconceptional exposure in 32.2 % and in utero exposure in 6.8 %; b) non-ionizing radiation; 54.2 % reported preconceptional exposure and in utero exposure at home; c) pregnancy-related problems: infections in 13.6 % (8 patients) and a prior history of miscarriage in 20.3 %; d) drugs/chemicals administered during pregnancy: capillary dye in 42.4 %, daily facial make-up in 45.8 %, antacids in 30.5 %, acetaminophen in 34 %, hormone therapy in 10 %, cocaine and marijuana consumption in 11.7 %; e) tobacco: exposure to active smoking in 93.2 % of patients; f) alcohol: in utero exposure in 6.8 %; g) occupational exposure in parents: paternal in 49 % of cases (hydrocarbons in 15, metal in 3, chemical in 2, timber in 2, and agriculture in 7). Four were exposed to pesticides, 3 to solvents, and 3 to paints; and maternal in 12 cases (20 %): low frequency non-ionizing radiation in 6 (textile in 5, and railway in 1), 5 in the service sector (2 hairdressers, 3 cleaners), and 1 the in chemical industry. In another 6 there was exposure to solvents and paints (footwear industry).

CONCLUSIONS

The hypotheses formulated in this observational study, which should be analyzed in future case-control and cohort studies, are: a) to scientifically document genetic-constitutional RF in the etiopathogenesis of NT; b) to determine the frequency and etiology of prior miscarriage and its possible association with NT; c) to determine the importance of active smoking before and during pregnancy as a RF for NT; d) to establish the importance of parental occupational exposure in the etiopathogenesis of NT; and e) to define more precisely the role of other physical and chemical RF in the development of NT. To determine and record the RF involved in the etiopathogenesis of NT, the environmental history should be documented in pediatric cancers. The identification of RF is one of the main objectives of Pediatric Environmental Health Specialty Units.

Personal and Occupational Exposure to Organic Solvents and Risk of Non-Hodgkin’s Lymphoma (NHL) in Women (United States)

OBJECTIVES

The authors assessed whether home and occupational exposure to organic solvents is associated with risk of NHL in women.

METHODS

A population-based, incidence case-control study was conducted in upstate New York, involving 376 NHL cases and 463 population controls selected from the Medicare beneficiary files and State driver's license records. Exposure information was obtained by telephone interview. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using an unconditional logistic regression model, adjusting for a number of risk factors for NHL.

RESULTS

Overall, history of exposure to organic solvents was not associated with the risk of NHL. A statistically significant increase in risk associated with occupational exposure was observed only for the subjects whose first exposure occurred before 1970 (OR=1.87, 95% CI 1.03-3.40). When occupational and home exposures to paint thinners/turpentine were combined and analyzed together, the risk of NHL associated with any exposure, compared to no exposure at either job or home, was a statistically significantly increased (OR=1.46, 95% CI: 1.05-2.03). This observation was more pronounced for B-cell lymphoma and for low-grade lymphoma with ORs of 1.52 (95 CI: 1.08-2.14) and 2.20 (95% CI; 1.42-3.41), respectively.

CONCLUSIONS

The results of this case-control study do support of a major role of organic solvents in the development of NHL among women currently living in the US. However, relatively intensive exposure in past occupations and use of paint thinners/turpentine may deserve further investigation.

Factores de riesgo para el neuroblastoma

INTRODUCTION

NB is the most frequent pediatric cancer arising in the sympathetic nervous system and represents a serious healthcare challenge because: 1) it is the most frequent neoplasm in the first decades of life; 2) it biological behavior is unpredictable (spontaneous regression, maturation to ganglioneuroma, and localized and metastasized variants); and 3) little is known about most of the risk factors involved in its etiopathogenesis. The objective of this study was to disseminate knowledge of constitutional and environmental (physical, chemical, biological and social) risk factors linked to the development of neuroblastoma (NB), with various levels of scientific evidence. To seek collaboration among pediatricians in the research project "Environment and Pediatric Cancer".

MATERIAL AND METHODS

We performed a systematic review of the literature published in the previous 25 years on risk factors for NB diagnosed in the first two decades of life, using Medline, the Science Citation Index and Embase. Search profiles were: "neuroblastoma/childhood sympathetic nervous system neoplasms and risk factors/etiology/epidemiology". The most interesting articles and the most relevant references contained therein were selected.

RESULTS

With greater or lesser scientific evidence, the following risk factors increase the risk of developing NB: genetic factors; geographic factors; ethnic factors; socioeconomic factors; infectious factors; physical factors; parental occupational exposure; gestational factors; and perinatal and maternal factors. Preventive factors associated with a lower risk of developing NB are breastfeeding and intake of vitamin supplements during pregnancy.

CONCLUSIONS

The main barriers to the identification of evidence-based risk factors involved in the development of NB are its complex biology and clinical course, its relative rarity and the difficulty of performing epidemiological studies. Research on constitutional and environmental factors involved in its etiopathogenesis should be stimulated. The best preventive strategy is to recommend breastfeeding for more than 6 months.

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.