Environews
NIEHS NEWS | Making Progress on Breast Cancer
Four Breast Cancer and the Environment Research Centers were funded by the NIEHS and the National Cancer Institute just over two years ago, after years of brainstorming on how to more effectively study the impact of environmental agents on breast cancer risk. This article (p. A98) describes presentations given at the centers' annual meeting in November 2005, where center investigators revealed findings from their research to date.
FOCUS | New Thinking on Neurodevelopment
We encounter known and suspected neurotoxicants at our work, in our use of everyday products such as household pesticides, and through the foods we eat. Pregnant women pass many of these exposures to their unborn children. Although not all exposures are permanently harmful, some can disrupt the nervous system, triggering an array of neurodevelopmental disorders. This article (p. A100) examines the connection between environmental exposures and neurodevelopmental consequences.
INNOVATIONS | Flu Vaccine Production Gets a Shot in the Arm
A global pandemic of avian flu is a very real possibility in the not-too-distant future. To help combat the threat of this and other potential pandemics, researchers are exploring ways to produce large amounts of vaccine as quickly as possible. One team has now contributed significantly to the fight by perfecting the reverse genetics method of mass-producing vaccine seed stock, described in this article (p. A108).
Commentaries
REMEDIATION | Elemental Mercury Spills
Causes of elemental mercury spills include improper storage, children playing, the breakage of devices, and ritualistic use of Hg0. Although inhalation is the primary exposure route, mercury released into the environment can enter water sources, where bacteria convert it into methylmercury, which accumulates in fish and other animals. Chronic exposure can damage the kidneys and neurologic system. Short-term exposure to high levels of vapors can cause lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation, among other effects. Baughman (p. 147) concludes that the best way to prevent Hg0 spills is not to store Hg0 in the home, school, or workplace.
ETHICS | Industry Science and Scientists
The chemical industry researches and tests products to implement product stewardship commitments and to ensure compliance with governmental requirements. Barrow and Conrad (p. 153) argue that a variety of mechanisms enable policy makers and the public to assure themselves that industry studies are identified as such, meet high scientific standards, and are not suppressed when findings are adverse to industry's interests. No federal laws, rules, or policies presume that scientific work should be ignored or given lesser weight because of the funding source.
Reviews
NEURODEGENERATIVE DISEASE | Pesticides and Parkinson's Disease
Exogenous toxicants, including pesticides, might be involved in the etiology of Parkinson's disease (PD), an idiopathic disease of the nervous system. Brown et al. (p. 156) present a comprehensive review of the published epidemiologic and toxicologic literature and critically evaluate whether a relationship exists between pesticide exposure and PD. The weight of evidence is sufficient to conclude that a generic association between pesticide exposure and PD exists, but is not sufficient for concluding that this is a causal relationship or that such a relationship exists for any particular pesticide or for a exposures to a pesticide and other exogenous toxicant.
NANOTECHNOLOGY | Toxicologic Review of Quantum Dots
Hardman (p. 165) reviews the growing applied science of nanotechnology, which has considerable global socioeconomic value; the benefits afforded by nanoscale materials and processes are expected to have significant impacts on almost all industries and all areas of society. With the nanotechnology economy estimated to be valued at $1 trillion by 2012, the prevalence of these materials in society will be increasing, as will the likelihood of exposures. Although they offer potentially invaluable societal benefits, such as drug targeting and in vivo biomedical imaging, quantum dots may also pose risks to human health and the environment under certain conditions.
Research
EXPOSURE ASSESSMENT | Blood Mercury in NHANES
Asians, Pacific Islanders, and Native Americans are a potentially high-risk group for dietary exposure to methylmercury through fish consumption. Blood mercury levels in this group were identified in recent reports of the National Health and Nutrition Examination Survey (NHANES) for the years 1999-2002. Hightower et al. (p. 173) found that subjects in NHANES who identified themselves as Asian, Pacific Islander, Native American, or multiracial had a higher prevalence of elevated blood mercury than all other racial/ethnic participants in the survey. Future studies should address reasons for the high mercury levels in this group and explore interventions for lowering risk of methylmercury exposure.
HUMAN TOXICOLOGY | Half-Lives of Hepta- to Deca-BDE in Human Serum
Occupational exposure to polybrominated diphenyl ethers (PBDEs) causes elevated serum levels of PBDEs in workers. PBDEs are also ubiquitous environmental contaminants found in the general population. Thuresson et al. (p. 176) modeled serum half-lives of PBDEs with 7-10 bromine substituents by performing nonlinear mixed-effects modeling of kinetics. Study results indicate that humans generally must be continuously exposed to BDE-209 to sustain the observed serum concentrations. BDE-209 is more readily transformed and/or eliminated than lower brominated diphenyl ether congeners; therefore, human health risk must be assessed accordingly.
EXPOSURE ASSESSMENT | Dermal Exposure to Jet Fuel
Jet propulsion fuel 8 (JP-8), the major jet fuel used worldwide, has been recognized as a major source of chemical exposure--both inhalation and dermal--for fuel-cell maintenance workers. Chao et al. (p. 182) investigated the contributions of dermal and inhalation JP-8 exposure to the total body dose of U.S. Air Force fuel-cell maintenance workers using naphthalene as a surrogate for JP-8 exposure. The results show that dermal exposure to JP-8 significantly contributes to the systemic dose and affects the levels of urinary naphthalene metabolites.
CARDIOVASCULAR DISEASE | Ischemic Heart Disease, Diabetes, and Wheat Agriculture
Schreinemachers (p. 186) examined ischemic heart disease and diabetes mortality in agricultural counties of Minnesota, Montana, North Dakota, and South Dakota, in association with environmental exposure to chlorophenoxy herbicides, using wheat acreage as a surrogate exposure. Data were collected on agricultural land use and 1979-1998 mortality from the U.S. Department of Agriculture and the Centers for Disease Control, respectively. Results suggest that mortality from acute myocardial infarction and type 2 diabetes increased and mortality from coronary atherosclerosis decreased in counties with large areas dedicated to spring and durum wheat farming. Firm conclusions on underlying causal inferences cannot be reached without more definitive studies.
TOXICOLOGY | Sex-Related Effects of Developmental PBDE Exposure
Increasing concentrations of polybrominated diphenyl ethers (PBDEs) in breast milk cause concern about possible developmental effects in nursed babies. Previous studies in rats have indicated effects on sex steroids and sexually dimorphic behavior after maternal exposure to polychlorinated biphenyls. Lilienthal et al. (p. 194) evaluated whether prenatal exposure to 2,2´,4,4´,5-pentabromodiphenyl ether (PBDE-99) induces similar endocrine-mediated effects. The results support the hypothesis that PBDEs are endocrine-active compounds and interfere with sexual development and sexually dimorphic behavior.
Also see Science Selections, p. A112
EXPOSURE ASSESSMENT | Human Dioxin Levels in Hong Kong
There are no previous reports from South China on chemically determined polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and other dioxin-like polychlorinated biphenyls (PCBs) in human breast milk expressed as World Health Organization (WHO) toxic equivalents. In an exposure study in Hong Kong, breast milk from 316 primiparous women were analyzed for PCDDs, PCDFs, and PCBs. Hedley et al. (p. 202) conclude that future international studies should incorporate a mother's age to allow standardization by other exposure factors and valid comparisons among countries. The findings provide support for the WHO breast-feeding advisory. Trends in human dioxin levels in the region cannot yet be determined; evaluation and interventions are needed to reduce emissions in China.
RESPIRATORY DISEASE | Assessment of Ozone-Induced Airway Inflammation
Single short-term exposures to ozone cause acute changes in pulmonary function and neutrophilic airway inflammation. Pulmonary function decrements are known to attenuate, but it is less clear how injury and inflammation are affected. Ratto et al. (p. 209) tested the hypothesis that neutrophils would increase after multiday exposure compared with single-day exposure. Using bronchoalveolar lavage, the researchers found a significant increase in the percentage of neutrophils and a significant decrease in the percentage of macrophages after 4 days compared with 1 day. Given that sputum induction likely samples proximal airways better than distal lung, these results support evidence that differential airway compartmental responses to O3 occur in humans and other species.
RISK ASSESSMENT | Nordic Dry-Cleaner Study
U.S. studies have reported an increased risk of esophageal and other cancers in dry cleaners exposed to tetrachloroethylene. Lynge et al. (p. 213) investigated whether the U.S. findings could be reproduced in the Nordic countries using a series of case-control studies nested in cohorts of laundry and dry-cleaning workers identified from the 1970 censuses of Denmark, Norway, Sweden, and Finland. They found no excess risk of esophageal cancer in Nordic dry cleaners, which differs from U.S. findings. These findings may be explained by chance, differences in tetrachloroethylene exposure levels, and/or confounding. The overall evidence on bladder cancer in dry cleaners is equivocal.
Also see Science Selections, p. A114
EXPOSURE ASSESSMENT | Human Exposure to Arsenic
Pellizzari and Clayton (p. 220) analyzed arsenate species in samples from the National Human Exposure Assessment Survey in U.S. Environmental Protection Agency Region 5 and the Children's Study (CS) in Minnesota. The CS study included drinking water, urine, hair, and dust, and both studies included food. Except for arsenobetaine (AsB) and arsenate [As(V)], the levels for As species measured in food and drinking water were very low or nonexistent. AsB was the most frequently detected form in food, whereas As(V) was only rarely detected. Thus, the predominant dietary exposure was an organic form of As. The major form of As in water was As(V), suggesting that food is primarily responsible for continual exposure.
RISK CHARACTERIZATION | Health Risks from Freshwater Bathing
Epidemiologic studies at public freshwater bathing sites in Germany were conducted to provide a better scientific basis for deriving recreational water quality standards. Unbiased concentration-response effects with no observed adverse effect levels (NOAELs) were demonstrated for three different definitions of gastroenteritis and four fecal indicator organisms. The standards are intended to protect the health of consumers who are not already immune or resistant to pathogens. In contrast to current World Health Organization recommendations, Wiedenmann et al. (p. 228) concluded that standards should be based on rates of compliance with NOAELs rather than on attributable risks determined above NOAELs, because these risks depend mainly on the unpredictable susceptibility of the cohorts.
NEURODEVELOPMENT | Fumonisin Exposure and Neural Tube Defects
The incidence of neural tube defects (NTDs) among women along the Texas-Mexico border doubled during 1990-1991. The outbreak began during the same crop year as an epizootic, which was attributed to exposue to fumonisin, a mycotoxin contaminate in corn. In populations consuming large quantities of corn, humans, as well as livestock, may be exposed to high levels of fumonisins. Using a population-based case-control study, Missmer et al. (p. 237) examined whether or not maternal exposure to fumonisins increases the risk of NTDs in offspring. Findings suggest that fumonisin exposure increases the risk of NTD, proportionate to dose, up to a threshold level, at which point fetal death may be more likely to occur.
RESPIRATORY DISEASE | Survival Analysis: Mortality and Air Pollution
In studies of associations between short-term air pollution and mortality, the unit of observation is the day rather than the individual. Also, assessment of individual risk factors is limited. Survival analysis may be more suitable when cohorts are examined with a time-dependent ecologic exposure. Lepeule et al. (p. 242) investigated the distribution over time of the short-term effect of black smoke and sulfur dioxide in Bordeaux, France, and identified a positive and significant association between cardiorespiratory mortality and black smoke. Results indicate that the Cox proportional hazards model is suitable to investigate simultaneously the short-term effect of air pollution and the effect of individual risk factors.
EXPOSURE ASSESSMENT | Residential Radio Frequency Exposures
Exposure to radio frequency (RF) nonionizing radiation from telecommunications is pervasive in modern society. Elevated disease risks have been reported in some populations exposed to radio and television transmissions, although findings are inconsistent. Burch et al. (p. 248) quantified RF exposures among 280 residents living near broadcasting transmitters in Denver, Colorado. RF power densities outside and inside each residence were obtained, and a global positioning system (GPS) identified geographic coordinates and elevations. Ressults demonstrate that both spatial and temporal factors contribute to residential RF exposure and that GPS/geographic information system technologies can improve RF exposure assessment and reduce exposure misclassification.
PROTEOMICS | Neonatal PBDE-99 Neurotoxicity
Exposure of mice to 2,2´,4,4´,5-pentabromodiphenyl ether (PBDE-99), a brominated flame retardant, during the brain growth spurt disrupts normal brain development and results in disturbed adult behavior. The neurodevelopmental toxicity of PBDE-99 affects the cholinergic and catecholaminergic systems. Alm et al. (p. 254) used a proteomics approach to study the early effect of PBDE-99 in the striatum and hippocampus of the neonatal mouse brain. They identified responses to early exposure to PBDE-99 that could contribute to persistent neurotoxic effects, and they show the usefulness of proteomics in identifying biomarkers for neurotoxicity of organohalogen compounds.
Also see Science Selections, p. A113
Children's Health
EXPOSURE ASSESSMENT | Children's Dietary Pesticide Exposure
Lu et al. (p. 260) used urinary biomonitoring to measure dietary exposure to organophosphorus (OP) pesticides in elementary school children. They substituted plant-derived foods in the children's conventional diets with organic food items for 5 consecutive days, then reverted to a conventional diet. Parents collected children's first-morning and before-bedtime urine samples throughout the 15-day study period. The median concentrations for OP pesticide metabolites, although not statistically significant, were lower on organic-diet consumption days. The researchers concluded that an organic diet provides a protective effect against exposures to OP pesticides used in agricultural production and that study children were most likely exposed to OP pesticides exclusively through their diet.
Also see Science Selections, p. A112
EXPOSURE ASSESSMENT | Dermal Transfer for Children
The major determinants of children's residential dermal exposure to pesticides have not been sufficiently evaluated. Cohen Hubal et al. (p. 264) studied a daycare center that had preexisting regular monthly pesticide applications in order to evaluate the feasibility of using empirically derived transfer coefficients to assess children's exposure to pesticides. Results indicate that the upper-range dermal transfer coefficient values from the study were similar to the default value used by the U.S. Environmental Protection Agency to assess children's dermal exposures resulting from contact with indoor surfaces.
ENDOCRINE SYSTEM | Phthalate Monoesters and Infant Hormones
Phthalates adversely affect the male reproductive system in animals. Main et al. (p. 270) investigated whether phthalate monoester contamination of human breast milk had any influence on the postnatal surge of reproductive hormones in newborn boys as a sign of testicular dysgenesis. They tested samples from a prospective Danish-Finnish cohort study on cryptorchidism from 1997 to 2001 and found all of the phthalate monoesters in breast milk, with large variations. The data on reproductive hormone profiles and phthalate exposures in newborn boys are in accordance with rodent data and suggest that human Leydig cell development and function may be vulnerable to perinatal exposure.
RESPIRATORY DISEASE | Case-Crossover Study of Infant Bronchiolitis
Karr et al. (p. 277) examined the association of infant bronchiolitis with acute exposure to ambient air pollutants, using a time-stratified case-crossover method, and they estimated the risk of bronchiolitis hospitalization associated with increases in wintertime ambient air pollutants by conditional logistic regression. Results provide little support for a link between acute increases in ambient air pollution and infant bronchiolitis, with the exception of PM2.5 exposure among premature infants. In these infants, the periods of viral acquisition and incubation concurred with the time of increased risk.
RESPIRATORY DISEASE | Traffic Influence on Lung Function in Children
Between 1991 and 2000, ambient air pollution in East Germany changed to resemble West German levels: the concentration of total suspended particles (TSPs) decreased on a broad scale while traffic increased. Sugiri et al. (p. 282) analyzed total lung capacity and airway resistance of German children. They used random effect models to determine the mutually adjusted association between lung function and short-term and chronic particle exposure and its interaction with living near a busy road. TSP exposure decreased on a broad scale. Lower concentrations of TSPs were associated with better measures of lung function; for children living near busy roads, this effect was diminished.
Mini-Monograph
HUMAN TOXICOLOGY | The four articles in the Mini-Monograph (p. 289, 290, 297, 302, and 307) represent a cross-section of results from human studies on mercury exposure and health outcomes presented at the most recent International Conference on Mercury as a Global Pollutant (ICMGP). The ICMGP was initiated in 1990 and is held every 2-3 years. The conference provides a needed global forum for presentation of scientific results, discussion, and the exchange of innovative ideas. In addition, it provides an opportunity to communicate research results to public policy makers, industry experts, and public representatives.