Environews
FOCUS | Benefits of Sunlight: A Bright Spot for Human Health
For several decades, public health messages about sunlight have focused on the hazards of overexposure, including skin cancer and eye damage. Although concern over these hazards is well deserved, our bodies—like plants—also obtain many benefits from moderate exposure to ultraviolet radiation from the sun. This article (p. A160) takes a look at the role of sunlight in human health and examines the question of how best to determine an optimal amount of sun exposure.
SPHERES OF INFLUENCE | Drought in the Southeast: Lessons for Water Management
Long accustomed to abundant rainfall and cheap water supplies, the southeastern United States now finds itself in the midst of an unprecedented drought that continues to severely tax one of its most precious resources. This article (p. A168) tells how some municipalities are responding to the drought, including which measures really help with conservation—and which ones don't.
Commentary
POPULATION HEALTH | NIEHS Extramural Global Environmental Health Portfolio
Global environmental health (GEH) is a critical topic for environmental health researchers and practitioners. The estimated environmental contribution of total worldwide disease burden is 25–33%. Drew et al. (p. 421) reviewed grants funded by the National Institute of Environmental Health Sciences (NIEHS) during fiscal years 2005–2008 to evaluate the costs and scientific composition of the GEH grant portfolio. The authors determined that, during this period, the NIEHS funded 57 scientific research projects in 37 countries, at an estimated cost of $30 million. Metals such as arsenic, methylmercury, and lead were the most frequently studied toxic agents, but a wide range of stressors, routes of exposure, and agents were also addressed. The portfolio analysis indicates that there is a firm foundation of research activities available to strengthen and encourage additional GEH partnerships.
Review
CANCER | Phytoestrogens and Breast Cancer Prevention
Phytoestrogens display an array of pharmacologic properties, and investigation of their potential as anticancer agents has increased dramatically in recent years. Mense et al. (p. 426) reviewed the published literature related to phytoestrogens and breast cancer and evaluated evidence regarding the possible mechanisms of phytoestrogen action. Evidence is inconconclusive regarding whether these plant compounds are chemoprotective or whether they may produce adverse outcomes related to breast carcinogenesis.
Research
CANCER | Keratin 6a Expression in Malignant Urothelium
Somji et al. (p. 434) used real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry to assess expression of keratin 6a in Cd2+- and As3+-transformed cells, corresponding heterotransplants, and human bladder cancer biopsy specimens. Compared with UROtsa cells grown in serum-containing growth medium alone, Cd2+- and As3+-transformed cells overexpressed keratin 6a mRNA and protein. Immunostaining of keratin 6a in tumor heterotransplants and some archival patient specimens of high-grade bladder cancer showed focal staining of the tumor cells that was localized to the cytoplasm. The authors suggest that keratin 6a expression may be a biomarker for malignant urothelial cells that possess an activated EGF and or insulin growth factor pathway.
MARINE SCIENCE | Sunscreens, Coral Bleaching, and Viral Infection
Coral bleaching (i.e., the release of coral symbiotic zooxanthellae) has negative impacts on biodiversity and functioning of reef ecosystems and on their production of goods and services. This increasing worldwide phenomenon is associated with temperature anomalies, high irradiance, pollution, and bacterial diseases. Personal care products, including sunscreens, have been shown to affect aquatic organisms much like other contaminants. According to Danovaro et al. (p. 441), sunscreens cause the rapid and complete bleaching of hard corals. The effect of sunscreens is due to organic ultraviolet filters, which induce the lytic viral cycle in symbiotic zooxanthellae with latent infections.
Also see Science Selections, p. A173
POPULATION HEALTH | Antimicrobial-Resistant Enterohemorrhagic E. coli in Potable Water
The contamination of processed or unprocessed drinking water by fecal coliforms has been reported worldwide. Despite a high incidence of waterborne diseases, enterohemorrhagic Escherichia coli (EHEC) are yet an underacknowledged pathogen of concern to public health in India. Although EHEC is present in surface water resources of India, drinking water sources are yet to be investigated. Ram et al. (p. 448) analyzed potable water samples for the presence of virulence determinants of EHEC and determined their sensitivity to antimicrobials. The occurrence of multiantimicrobial-resistantEHECin potable water is an important health concern because of the risk of waterborne outbreaks.
EXPOSURE ASSESSMENT | Ozone, Secondary Particles, and Mortality
Although a positive association has been found between ambient ozone and mortality, the observed effect may be confounded by other secondary pollutants that are produced concurrently with ozone. Franklin and Schwartz (p. 453) used time-series models fit to 3–6 years of data for 2000–2005 from 18 U.S. communities to address the question of whether the ozone–mortality relationship is entirely a reflection of the adverse effect of ozone, or whether it is, at least in part, an effect of other secondary pollutants. The results demonstrate that some of the excess mortality associated with ambient ozone could actually represent the effects of secondary sulfate particles.
RISK ASSESSMENT | Epidemiologic Analyses Using Source-Apportioned Fine PM
Interest in health effects of particulate matter (PM) has focused on identifying sources of PM, including biomass burning, power plants, and gasoline and diesel emissions that may be associated with adverse health. However, few epidemiologic studies have included source-apportionment estimates in their examinations of PM health effects. Sarnat et al. (p. 459) analyzed a time series of chemically speciated PM measurements in Atlanta, Georgia, and conducted an epidemiologic analysis using data from three distinct source-apportionment methods. In spite of differences among these methods, the findings suggest that modeled source-apportioned data can be used to produce robust estimates of acute health risk.
BIOMONITORS | Phthalate Exposure and Variability in Pregnancy
Although urinary concentrations of phthalate metabolites are frequently used as biomarkers in epidemiologic studies, variability during pregnancy has not been characterized. Adibi et al. (p. 467) measured phthalate metabolite concentrations in spot urine samples collected from 246 pregnant Dominican and African-American women. Urinary concentrations of diethyl phthalate and di-2-ethylhexyl phthalate metabolites in pregnant women showed lower reproducibility than metabolites for di-n-butyl phthalate and butylbenzyl phthalate. A single indoor air sample may be sufficient to characterize phthalate exposure in the home, whereas urinary phthalate biomarkers should be sampled longitudinally during pregnancy to minimize exposure misclassification.
CARDIOVASCULAR DISEASE | PCBs Alter Stroke Outcome
The "developmental origins of adult disease" hypothesis, which was originally derived from evidence linking low birth weight to cardiovascular diseases including stroke, has now been expanded to include developmental exposures to environmental contaminants as risk factors for adult-onset disease. Dziennis et al. (p. 474) tested the hypothesis that developmental exposure to polychlorinated biphenyls (PCBs) alters stroke outcome in adults. Rats were exposed throughout gestation and lactation to the PCB mixture Aroclor 1254 in the maternal diet. The data show that developmental exposures to environmental contaminants can influence the response of the adult brain to ischemic injury and thus represent potentially important determinants of stroke susceptibility.
CARDIOVASCULAR DISEASE | Traffic Air Pollution and Heart Failure Survival
Patients with heart failure (HF) have been found to be particularly susceptible to the acute effects of air pollution; however, little is known about the long-term effects of air pollution exposure on patients with this increasingly prevalent disease. In their examination of the mortality risk associated with residential exposure to traffic-related air pollution among HF patients, Medina-Ramón et al. (p. 481) found that residential exposure to traffic-related air pollution increases the mortality risk after hospitalization with acute HF. Reducing exposure to traffic-related emissions may improve the long-term prognosis of HF patients.
CARDIOVASCULAR DISEASE | Particulate Matter Exposure and Blood Pressure
Blood pressure (BP) may be implicated in associations between ambient particulate matter (PM) and cardiovascular morbidity and mortality. Auchincloss et al. (p. 486) examined cross-sectional associations between short-term ambient fine particles (≤ 2.5 µm in aerodynamic diameter; PM2.5) and BP parameters [systolic blood pressure (SBP), diastolic blood pressure, mean arterial pressure, and pulse pressure (PP)] in 5,112 subjects 45–84 years of age from the Multi-Ethnic Study of Atherosclerosis cohort. Higher SBP and PP were associated with ambient levels of PM2.5; the association was stronger in the presence of roadway traffic, suggesting that impairment of blood pressure regulation may play a role in response to air pollution.
HEALTH POLICY | Agricultural Output after Pesticide Bans
The pesticides monocrotophos, methamidophos, and endosulfan were a very common cause of severe poisoning in Sri Lanka during the 1980s and early 1990s, before they were banned. These bans, in 1995 and 1998, were followed by a very large reduction in both fatal poisonings and suicide. At present, the most commonly used insecticides in Sri Lanka are the less toxic World Health Organization Class II organophosphorus pesticides and carbamates. Manuweera et al. (p. 492) compared data on crop yields in Sri Lanka with those from surrounding South Asian countries to determinewhether the bans adversely affected agricultural production or costs. Results showed no drop in productivity in the years after the main bans were instituted. Therefore, countries aiming to reduce deaths from pesticide poisoning should evaluate agricultural needs and develop a plan that encourages substitution of less toxic pesticides.
NANOTECHNOLOGY | Nanotube Bioaccumulation by Lumbriculus variegatus
Carbon nanotubes represent a class of nanomaterials having broad application potentials and documented cellular uptake and ecotoxicologic effects that raise the possibility that they may bioaccumulate in living organisms. Petersen et al. (p. 496) used radioactively labeled nanotubes synthesized using a novel methane chemical vapor deposition procedure. Single-walled and multiwalled carbon nanotubes and pyrene were spiked to sediment samples, and the respective uptake and depuration were assessed using the oligochaete Lumbriculus variegatus. The researchers suggest that, unlike polycyclic aromatic hydrocarbons, purified carbon nanotubes do not readily absorb into organism tissues.
GENE POLYMORPHISM | Arsenic-Metabolizing Genes and Susceptibility
Individual susceptibility to arsenic-induced skin lesions and skin cancer may be affected by individual variabilities in arsenic metabolism. Metabolism of arsenic, which proceeds through sequential reduction and oxidative methylation, is mediated by four genes; alteration in functions of gene products may lead to arsenic-specific disease manifestations. De Chaudhuri et al. (p. 501) screened all the exons in these genes in an arsenic-exposed population to find any probable association between arsenicism and exonic single nucleotide polymorphisms. Results indicate that the three purine nucleoside phosphorylase variants render individuals susceptible to developing arsenic-induced skin lesions.
COMPUTATIONAL BIOLOGY | Biological Descriptors in QSAR Modeling of Carcinogenicity
The National Toxicology Program (NTP), in collaboration with the National Center for Chemical Genomics, has initiated a project on high-throughput screening (HTS) of environmental chemicals to develop efficient approaches for rapid evaluation of chemical toxicity and human health risk of environmental compounds. Zhu et al. (p. 506) used the k nearest neighbor quantitative structure–activity relationship (QSAR) modeling method to explore these data in terms of their utility for predicting adverse health effects of the environmental agents. The prediction accuracy of the model was significantly improved (72.7%) when chemical descriptors were augmented by HTS data, which were regarded as biological descriptors. Combining NTP–HTS profiles with conventional chemical descriptors could considerably improve the predictive power of computational approaches in toxicology.
IMMUNOLOGY | Prenatal and Postnatal Exposure to BPA on Immunity
Bisphenol A (BPA) is a widespread endocrine-disrupting chemical that can affect humans and animals. Yan et al. (p. 514) investigated the effects of adult or prenatal exposure to BPA on T-helper 1/T-helper 2 (TH1/TH2) immune responses and the mechanisms underlying these effects. To evaluate the effects of BPA exposure in adulthood, male Leishmania major–susceptible BALB/c and –resistant C57BL/6 mice were injected with BPA before being infected with L. major. For prenatal exposure, female mice were given BPA-containing drinking water, mated, and then given BPA for another week. The researchers found that BPA promotes the development of TH2 cells in adulthood and both TH1 and TH2 cells in prenatal stages by reducing the number of regulatory T cells.
CARDIOVASCULAR DISEASE | Angiogenic Potential of Roxarsone
Roxarsone (3-nitro-4-hydroxy benzene arsonic acid) is an arsenic compound widely used in the poultry industry as a feed additive to prevent coccidiosis, to stimulate growth, and to improve tissue pigmentation. Little is known about the potential human health effects from roxarsone released into the environment from chicken waste or from residual compounds in chicken products. Basu et al. (p. 520) used cultured human aortic endothelial cells to investigate the angiogenic potential of roxarsone compared with that of inorganic arsenite (AsIII). The results demonstrate that roxarsone and AsIII promote angiogenic phenotype in human endothelial cells through distinctly different signaling mechanisms.
GENE EXPRESSION | Arsenic Exposure Modulates Gene Expression in Humans
Arsenic exposure impairs development and can lead to cancer, cardiovascular disease, and diabetes. Drinking-water arsenic levels are above the current recommended maximum contaminant level of 10 µg/L in the northeastern, western, and north central regions of the United States, primarily because of geologic sources of contamination. Andrew et al. (p. 524) used Affymetrix microarray-based genomewide analyses of expression patterns associated with internal biomarkers of arsenic exposure to investigate the effects of arsenic exposure at levels relevant to U.S. populations. Findings define biologic changes that occur with chronic arsenic exposure in humans, and provide leads and potential targets for understanding and monitoring the pathogenesis of arsenic-induced diseases.
Environmental Medicine
REPRODUCTIVE HEALTH | Arsenic Exposure and Erectile Dysfunction
Erectile dysfunction (ED) has a profound impact on the quality of life of many men. Risk factors associated with ED include aging, sex hormone levels, hypertension, cardiovascular disease, and diabetes mellitus. Arsenic exposure could damage peripheral vessels and increase the risk of cardiovascular disease, but few studies have evaluated the relationship between arsenic exposure and ED. Hsieh et al. (p. 532) investigated whether exposure to arsenic enhances the risk of ED in men ≥ 50 years of age, comparing men from an arsenic-endemic area with those from a non–arsenic-endemic area. The authors found that the prevalence of ED was greater in men from the arsenic-endemic area. Subjects with arsenic exposure > 50 ppb had a significantly higher risk of developing ED than those with exposure < 50 ppb.
Also see Science Selections, p. A172
Children's Health
EXPOSURE ASSESSMENT | Children's Longitudinal OP Pesticide Exposure
The widespread use of organophosphorus (OP) pesticides has led to frequent exposure in adults and children. Because such exposure may cause adverse health effects, particularly in children, the sources and patterns of exposure need further study. Lu et al. (p. 537) assessed young urban/suburban children's longitudinal exposure to OP pesticides in the Children's Pesticide Exposure Study, conducted in the greater Seattle, Washington, area, using a novel study design that allowed them to determine the contribution of dietary intake to the overall OP pesticide exposure. Their findings demonstrate that dietary intake of OP pesticides represents the major source of exposure in young children.
Also see Science Selections, p. A172
FETAL DEVELOPMENT | Cooking Fuel Exposure and Low Birth Weight
Maternal exposure to wood fuel smoke may lead to impaired fetal growth due to hypoxia or oxidative stress from smoke constituents such as carbon monoxide and particulate matter. Siddiqui et al. (p. 543) studied the risk of low birth weight (LBW) and reduced mean birth weight in relation to reported use of wood or natural gas for cooking during the prenatal period. Cooking with wood fuel during pregnancy was associated with LBW and marginally lower mean birth weight compared with using natural gas.
Also see Science Selections, p. A173
ASTHMA | Air Pollution and FEV1 in Children with Asthma
Epidemiologic studies have shown associations between asthma outcomes and outdoor air pollutants such as nitrogen dioxide and particulate matter < 2.5 µm in diameter (PM2.5). Independent effects of specific pollutants have been difficult to detect because most studies have relied on highly correlated central site measurements. Delfino et al. (p. 550) evaluated the relationship of daily changes in percent-predicted forced expiratory volume in 1 sec (FEV1) to personal and ambient air pollutant exposures. Independent pollutant associations with lung function could be missed using ambient data alone. Different sets of causal components are suggested by independence of FEV1 associations with personal PM2.5 mass from associations with personal NO2.
CANCER | Agricultural Pesticides and Childhood Cancers
The potential for widespread exposure to agricultural pesticides through drift during application raises concerns about possible health effects to exposed children living in areas of high agricultural activity. Carozza et al. (p. 559) evaluated whether residence in a county with greater agricultural activity was associated with risk of developing cancer in children < 15 years of age. The results show statistically significant increased risk estimates for many types of childhood cancers associated with residence at diagnosis in counties having a moderate to high level of agricultural activity, with a remarkably consistent dose–response effect seen for counties having ≥ 60% of the total county acreage devoted to farming.
REPRODUCTIVE HEALTH | Reproductive Development in Sons of Female Greenhouse Workers
Andersen et al. (p. 566) investigated whether occupational pesticide exposure during pregnancy causes adverse effects on the reproductive development in the sons. Pregnant women employed in greenhouses in Denmark were consecutively recruited, and 113 mother–son pairs were included. The mothers were categorized as occupationally exposed or unexposed to pesticides during pregnancy. Testicular position and volume, penile length, and position of urethral opening were determined for each child at 3 months of age using standardized techniques. The findings suggest an adverse effect of maternal occupational pesticide exposure on reproductive development in the sons in spite of current greenhouse safeguards and special measures to protect pregnant women.
