Environews
FOCUS | Synthetic Turf: Health Debate Takes Root
Given the rising obesity epidemic and its resultant health effects, anything that can increase physical activity would seem like a good thing. Many municipalities are turning to synthetic turf as a way to make athletic fields available for more months of the year as well as reduce chemical use and maintenance. But some scientists, law makers, and residents wonder if synthetic turf may itself contribute to adverse health effects, with the rubber infill and silica sand used in some products being the main source of concern for potential health effects. This article (p. A116) takes a look at the positive and negative impacts of artificial grass.
SPHERES OF INFLUENCE | Chemical Reaction: The U.S. Response to REACH
Prevention of health hazards that could accompany exposure to certain chemicals is a priority the European Union is assigning to the companies that produce or market those chemicals in Europe. This article (p. A124)discusses how Europe's REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) legislation is setting new standards for chemical regulation by requiring companies to provide more information on the chemicals they supply to ensure that informed decisions can be made regarding use.
Reviews
REPRODUCTIVE HEALTH | INUENDO Summary Review
Bonde et al. (p. 269) synthesized the main findings from an international epidemiologic study on the impact of biopersistent organic pollutants (POPs) on human reproductive function. No direct evidence of hormone-like activity was found for the polychlorinated biphenyl congener CB-153 or for the main metabolite of dichlorodiphenyltrichloroethane (DDT), p,p´-DDE, because serum concentrations of these compounds were not consistently related to either endogenous or exogenous hormone activity in serum. Nevertheless, several links were identified between POPs exposure and biomarkers of male reproductive function. Despite these effects, the fertility in terms of time taken to conceive was not related to POPs except in Greenlandic Inuits.
REMEDIATION | Phytostabilization of Mine Tailings
Unreclaimed mine tailings sites are a worldwide problem, with thousands of unvegetated, exposed tailings piles presenting a source of contamination for nearby communities. Tailings disposal sites in arid and semiarid environments are especially subject to eolian dispersion and water erosion. Mendez and Maier (p. 278) reviewed phytostabilization (the use of plants for in situ stabilization of tailings and metal contaminants) as a feasible alternative to costly remediation practices. Results indicate that phytostabilization has promising potential, but long-term studies will be needed to expand knowledge of suitable plant species and mine tailings chemistry.
Research
TOXICOLOGY | Compound Cytotoxicity Profiling Using qHTS
Animal-based test methods are often used to evaluate the propensity of compounds to produce adverse health effects in humans. Although useful, these methods are relatively expensive and low-throughput. Also, differences in species biology may confound extrapolation to human health effects. In a collaboration between the National Toxicology Program and the National Institutes of Health Chemical Genomics Center, Xia et al. (p. 284) investigated a battery of cell-based screens to prioritize compounds for further toxicologic evaluation. The generation of high-quality cytotoxicity data on a library of known compounds using quantitative high-throughput screening (qHTS) demonstrates the potential of this methodology to profile a broader array of assays and compounds.
INFECTIOUS DISEASE | Size Distribution of Airborne Microorganisms
The distribution of microorganisms, and especially pathogens, over airborne particles of different sizes could have significant implications regarding the dispersion of these microorganisms across the planet, thus affecting human health. To determine the size distribution of microorganisms in the air, Polymenakou et al. (p. 292) examined the microbial quality of the aerosols over the eastern Mediterranean region during an African storm. Bacterial communities associated with aerosol particles of six different size ranges were characterized following molecular culture–independent methods. The presence of aerosolized bacteria in small-size particles may have significant implications to human health via intercontinental transportation of pathogens.
Also see Science Selections, p. A128
POPULATION HEALTH | Outcomes of the California Ban on Pharmaceutical Lindane
There are increasing concerns over the presence and implications of pharmaceutical agents in water. Because of adverse effects on water quality, in 2002 California banned the pharmaceutical use of lindane, which is used as a treatment for head lice and scabies. Humphreys et al. (p. 297) describe the effects the ban has had on wastewater quality, unintentional exposures, and clinical practice. Because this is the first time a pharmaceutical has been outlawed to protect water quality, this ban provides a rare opportunity to evaluate the possible or potential outcomes of future public health interventions aimed at reducing pharmaceutical water contamination.
Also see Science Selections, p. A128
EXPOSURE ASSESSMENT | Reference Range of Triclosan Urinary Concentrations in the United States
Triclosan, a synthetic chemical with broad antimicrobial activity, has been used extensively in consumer products, including personal care products, textiles, and plastic kitchenware. Calafat et al. (p. 303) assessed exposure to triclosan in a representative sample ≥ 6 years of age of the U.S. general population from the 2003–2004 National Health and Nutrition Examination Survey (NHANES). Triclosan was detected in about three-fourths of urine samples analyzed. Triclosan concentrations differed by age and socioeconomic status but not by race/ethnicity and sex. The concentrations of triclosan appeared to be highest during the third decade of life and among people with the highest household incomes.
REPRODUCTIVE HEALTH | PBDE-47 Alters Reproductive System of Female Rats
Polybrominated diphenyl ethers (PBDEs) are capable of disrupting thyroid hormone homeostasis. PBDE-47 is one of the most abundant congeners found in human breast adipose tissue and maternal milk samples. Talsness et al. (p. 308) evaluated the effects of developmental exposure to low doses of PBDE-47 on the female reproductive system of rats. The authors observed alterations in ovarian folliculogenesis, circulating estradiol concentrations, and persistent changes to both the ovaries and thyroid glands in the offspring. No relevant changes in reproductive indices were observed after the exposed F1 females were mated with nontreeated males.
METABOLISM | Nutrition and Arsenic in Bangladeshi Women
The interindividual variation in metabolism of inorganic arsenic (iAs), involving methylation via one-carbon metabolism, has been well documented, but the reasons remain unclear. To elucidate the effect of nutrition on As methylation among women in Matlab, Bangladesh, where people are chronically exposed to iAs via drinking water, Li et al. (p. 315) studied effects of macronutrient status using body mass index among women in early pregnancy [gestational week (GW) 8], and effects of micronutrient status among women at GW14. In spite of the high As exposure and prevalent malnutrition, overall As methylation in women in early pregnancy was remarkably efficient. Among the factors studied, As exposure level had the greatest impact on As methylation.
ENDOCRINE SYSTEM | Adverse Effects of Phytoestrogen-Free Feed
Although estrogenic chemicals can disrupt development of the reproductive system, there is debate about whether phytoestrogens in soy are beneficial, benign, or harmful. Ruhlen et al. (p. 322) compared reproductive and metabolic characteristics in male and female mice reared and maintained on non-soy low-phytoestrogen feed or soy-based high-phytoestrogen feed. Removing phytoestrogens from the feed produced an obese phenotype consistent with metabolic syndrome, and the associated reproductive system abnormalities are consistent with fetal estrogenization syndrome caused by elevated endogenous fetal estradiol. Laboratory rodents may have become adapted to high-phytoestrogen intake; thus, removing all phytoestrogens may lead to alterations that could disrupt many types of biomedical research.
CARDIOVASCULAR DISEASE | Hypertension and Exposure to Noise Near Airports
Recent studies indicate that noise exposure may cause hypertension, an important risk factor for cardiovascular disease. To assess the relationship between noise from aircraft, as well as road traffic near airports, and the risk of hypertension, Jarup et al. (p. 329) measured blood pressure and collected data on health, socioeconomic, and lifestyle factors for people who had lived near any of six major European airports for at least 5 years. Results indicate excess risks of hypertension related to long-term noise exposure, primarily for night-time aircraft noise and daily average road traffic noise.
BIOMONITORS | Phthalates in Milk, Blood, and Urine from Nursing Mothers
To investigate whether phthalates pose a risk for perinatal developmental effects, Högberg et al. (p. 334) measured the concentrations of phthalate diesters or their metabolites in breast milk, blood, and urine and evaluated their suitability for assessing perinatal exposure to phthalates. The authors found that concentrations of phthalate metabolites in urine are more informative than those in milk or blood. However, because of discomfort and potential technical problems such as contamination, sampling of breast milk or blood and analysis for phthalates is not recommended. Although urine is a suitable matrix for health-related phthalate monitoring, urinary concentrations in nursing mothers cannot be used to estimate exposure to phthalates through milk ingestion by breast-fed infants.
NEURODEVELOPMENT | Diazinon Developmental Neurotoxicity
The developmental neurotoxicity of organophosphate pesticides involves mechanisms other than their shared property of cholinesterase inhibition. Slotkin et al. (p. 340) treated newborn rats with diazinon (DZN) on postnatal days 1–4, using doses spanning the threshold for barely detectable cholinesterase inhibition. Results indicate thatdevelopmental exposures toapparently nontoxic doses of DZN compromise neural cell development and alter acetylcholine synaptic function in adolescence and adulthood. The patterns are substantially different from those seen in earlier work with chlorpyrifos, reinforcing the concept that the various organophosphates have fundamentally different effects on the developmental trajectories of specific neurotransmitter systems, unrelated to their shared action as cholinesterase inhibitors.
BIOSENSORS | Transgenic Mice for Monitoring of Air Pollution
The aryl hydrocarbon receptor (AhR) plays crucial roles in toxicologic responses of animals to environmental pollutants, especially halogenated and polycyclic aromatic hydrocarbons. To assess the risk of air pollution using biological systems, Kasai et al. (p. 349) generated transgenic sensor mice that produce secreted alkaline phosphatase under the control of AhR. This study demonstrates direct, comprehensive monitoring of air pollution using genetically engineered mammals. This system should be useful for real risk assessment of halogenated and polycyclic aromatic hydrocarbons in the air, especially in environments containing cigarette smoke.
NEURODEVELOPMENT | Gestational Lead-Induced Effects in Aged Male Mice
Low-level developmental lead exposure is linked to cognitive and neurologic disorders in children. However, the long-term effects of gestational lead exposure (GLE) have received little attention. Leasure et al. (p. 355) established a murine model of human equivalent GLE and determined dose–response effects on body weight, motor functions, and dopamine neurochemistry in 1-year-old offspring. The results show that GLE produced permanent male-specific deficits. The nonmonotonic dose-dependent responses showed that low-level GLE produced the most adverse effects. These data reinforce the idea that lifetime measures of dose–response toxicant exposure should be a component of the neurotoxic risk assessment process.
Also see Science Selections, p. A129
FETAL DEVELOPMENT | The Effect of Ambient Air Pollution on Fetal Ultrasonic Measurements
Over the past decade there has been mounting evidence that ambient air pollution during pregnancy influences fetal growth. Hansen et al. (p. 362) examined possible associations between fetal ultrasonic measurements collected from 15,623 scans (13–26 weeks gestation) and ambient air pollution during early pregnancy. The average monthly exposures of the mothers over the first 4 months of pregnancy were calculated for PM10 (particulate matter < 10 µg in aerodynamic diameter), ozone, nitrogen dioxide, and sulfur dioxide. Final analyses included scans from only those women within 2 km of an air pollution–monitoring site. The authors found strong effects of ambient air pollution on ultrasound measures.
CANCER | Benzene and Leukemia Mortality
Exposure to benzene, a human carcinogen, occurs in occupational and environmental settings. To investigate variations in benzene-related leukemia with age at exposure and time since exposure, Richardson (p. 370) evaluated data from a cohort of 1,845 rubber hydrochloride workers. The author estimated benzene exposure–leukemia mortality trends by applying proportional hazards regression methods, and assessed temporal variation in the impact of benzene on leukemia rates via exposure time windows and fitting of a multistage cancer model. Results showed that leukemia was more strongly associated with benzene exposures at ≥ 45 years of age than with exposures at younger ages. Further attention should be given to evaluating the susceptibility of older workers to benzene-induced leukemia.
CARDIOVASCULAR DISEASE | Vascular Effects of Ultrafine Particles
Ultrafine particles (UFPs) may contribute to the cardiovascular effects of exposure to particulate air pollution, in part because of their relatively efficient alveolar deposition and potential to enter the pulmonary vascular space. Shah et al. (p. 375) tested the hypothesis that inhalation of elemental carbon UFPs alters systemic vascular function. Sixteen healthy subjects inhaled air or 50 µg/m3 elemental carbon UFPs by mouthpiece for 2 hr while exercising intermittently. Inhalation of 50 µg/m3 carbon UFPs during intermittent exercise impairs peak forearm blood flow during reactive hyperemia in healthy human subjects.
RESPIRATORY DISEASE | Sensitization Alters OP-Induced Hyperreactivity
Sensitization to allergen is a significant contributing factor in asthma, and sensitization changes virus-induced airway hyperreactivity from an eosinophil-independent mechanism to one mediated by eosinophils. Using guinea pigs, Proskocil et al. (p. 381) investigated whether sensitization similarly influences airway hyperreactivity induced by organophosphorus pesticides (OPs). The authors found that antigen sensitization increases vulnerability to parathion-induced airway hyperreactivity and changes the mechanism to one that is dependent on interleukin-5. Because sensitization to allergens is characteristic of 50% of the general population and 80% of asthmatics (including children), these findings have significant implications for OP risk assessment, intervention, and treatment strategies.
ENDOCRINE SYSTEM | Variability in Phytoestrogen Content of Animal Feed
Heindel and vom Saal (p. 389) report on two National Institutes of Health–sponsored workshops that were held to address whether dietary estrogens could significantly impact end points in experimental animals, and to involve program participants and feed manufacturers in addressing the problems associated with measuring and eliminating batch-to-batch variability of estrogenic content in rodent diets that may result in conflicting findings in animal experiments within and between laboratories. Participants recommended that researchers carefully choose a diet with estrogenic activity (or lack thereof) that is appropriate for the experimental model and end points of interest. This will require manufacturers of laboratory animal diets to provide information on content of phytoestrogens and other estrogenic compounds in commercial diets used in animal research.
Children's Health
EXPOSURE ASSESSMENT | Renal Effects of Dental Amalgam in Children
Mercury is nephrotoxic, and dental amalgam is a source of mercury exposure. Children 6–10 years of age, with two or more posterior teeth with caries but no prior amalgam restorations, were randomized to one of two treatments—amalgam or resin composite (white fillings)—used for caries treatment during 5 years of follow-up. Barregard et al. (p. 394) found no significant differences between treatment groups in average levels of renal biomarkers or in significant effects of number of dental amalgams on these markers. However, they found a significantly increased prevalence of microalbuminuria among children in the amalgam group in years 3–5.
Also see Science Selections, p. A129
EXPOSURE ASSESSMENT | PBDEs and Hydroxylated PBDE Metabolites in Young Humans
To investigate polybrominated diphenyl ethers (PBDEs) and the presence of hydroxylated metabolites, Athanasiadou et al. (p. 400) assessed pooled serum samples obtained from children 11–15 years of age who had been potentially highly exposed to PBDEs while working as scrap scavengers at a large municipal waste disposal site in Managua, Nicaragua. The children who lived and worked at the waste disposal site had very high levels of medium brominated diphenyl ethers, whereas the levels observed in the referent children were comparable to contemporary observations in the United States. The exposure pattern was consistent with dust being the dominating source, and the children with the highest PBDE levels also had the highest levels of hydroxylated metabolites.
ASTHMA | Asthma, Wheezing, GSTP1, Haplotypes
Glutathione S-transferase P1 (GSTP1) plays a role in a spectrum of respiratory diseases; however, the effects of sequence variation across the entire locus in asthma pathogenesis have yet to be determined. To investigate whether sequence variations in the GSTP1 coding and promoter regions are associated with asthma and wheezing outcomes and to determine whether variants affect susceptibility to maternal smoking, Li et al. (p. 409) assessed the associations of GSTP1 variants with asthma and wheezing among white children in the Children's Health Study. Variants in both the promoter and coding regions of the GSTP1 locus may contribute to the occurrence of childhood asthma and wheezing and may increase susceptibility to adverse effects of tobacco-smoke exposure.
ENDOCRINE SYSTEM | Estrogen-Related Physical Findings in Infants
Soy formula containing estrogenic isoflavones is widely used in the United States, and infants who consume soy formula exclusively have high isoflavone exposures. Bernbaum et al. (p. 416) used measures of breast and genital development to determine whether soy formula prolonged the physiologic estrogenization of newborns. Breast tissue was maximal at birth and disappeared in older children, which is consistent with waning maternal estrogen; genital development did not change by age; breast milk secretion and withdrawal bleeding were unusual; vaginal wall cells showed maximal estrogen effect at birth, then reverted; and girls on soy formula appeared to show reestrogenization at 6 months of age. Measurement of breast tissue and characterization of vaginal wall cells could be used to evaluate exposures with estrogen-like effects.