Environews
FOCUS | Unwelcome Guest: PBDEs in Indoor Dust
Researchers have known for years that house dust is a major exposure route for lead and certain pesticides. Now attention is turning to another class of dustborne chemicals: brominated flame retardants, specifically polybrominated diphenyl ethers (PBDEs). Research indicates that many of the consumer products in homes, cars, and workplaces release these chemicals, but hard data on their human health effects are only just beginning to emerge. This article (p. A202) describes possible routes of exposure to PBDEs and examines some of the dangers they may pose to human health.
INNOVATIONS | New Thinking on Flame Retardants
When upholstered furniture catches on fire, it's a big deal: burning foam cushioning can quickly lead to "flashover," in which nearly everything combustible inside a room ignites simultaneously. Flame-retardant chemicals help lessen the potential for a fire, but with these protective measures comes the risk of adverse human health effects. This article (p. A210) describes how concern regarding the toxicity of flame retardants is driving the movement toward new performance standards as well as the search for new flame retardants that are as safe as they are effective.
Commentaries
TOXICOLOGY | Molecular Modeling for Prioritizing Bioassays
The human health risk from exposure to environmental chemicals often must be evaluated when relevant elements of the preferred data are unavailable. Therefore, strategies are needed to predict this information and prioritize the outstanding data requirements for the risk evaluation. Molecular modeling methods can be adapted to study the interactions of environmental chemicals with biomolecular targets. Rabinowitz et al. (p. 573) provide an overview of the challenges that arise from applying molecular modeling tools developed and commonly used for pharmaceutical discovery to the problem of predicting the potential toxicities of environmental chemicals.
CLIMATE CHANGE | Global Farm Animal Production and Climate Change
The farm animal production sector is the single largest anthropogenic user of land, contributing to many environmental problems, including global warming and climate change. Koneswaran and Nierenberg (p. 578) analyzed scientific literature on farm animal production and documented greenhouse gas emissions, as well as various mitigation strategies. An analysis of agricultural products encompasses not only the care and feeding of animals but also waste storage and disposal, water use, and energy used to conduct such activities. Mitigating and preventing environmental harms caused by the farm animal sector require immediate and substantial changes in regulation, current animal agriculture practices, and consumption patterns.
Review
HEALTH POLICY | Conceptual Model of Research Metrics
Federal, state, and private research agencies and organizations have faced increasing administrative and public demand for performance measurement. Historically, performance measurement consisted predominantly of near-term outputs measured through bibliometrics. The recent focus is on accountability for investment based on long-term outcomes. Developing measurable outcome-based metrics for research programs has been particularly challenging because of difficulty linking research results to spatially and temporally distant outcomes. Engel-Cox et al. (p. 583) developed a logic model to define the components and linkages between environmental health research programs and improvements in human health, the environment, and the economy.
Research
PARKINSON DISEASE | Neurotoxicity of fMLP via Microglial Activation
Parkinson disease (PD), a chronic neurodegenerative disease, has been proposed to be a multifactorial disorder resulting from a combination of normal aging, genetic deficits, and environmental mechanisms (chemical, infectious, and traumatic). Microglial activation is important in the pathogenesis of PD. Gao et al. (p. 593) investigated dopaminergic (DA) neurotoxicity and the underlying mechanisms of formyl-methionyl-leucyl-phenylalanine (fMLP), a bacteria-derived peptide, in relation to PD. fMLP induces DA neurotoxicity through activation of microglial PHOX (phagocyte oxidase) and subsequent production of superoxide, suggesting a role of fMLP in the central nervous system inflammatory process.
REPRODUCTIVE HEALTH | PCBs/PCDFs and Prolonged Time to Pregnancy in Women
Polychlorinated biphenyls (PCBs), dibenzofurans (PCDFs), and dibenzodioxins (PCDDs) may affect the female reproductive system in animals and humans. In 1978–1979, a mass poisoning occurred in central Taiwan due to PCB/PCDF-contaminated cooking oil (called Yucheng, or oil disease in Chinese). Yang et al. (p. 599) studied exposed women to determine whether PCB/PCDF exposure affected fertility. The researchers found prolonged time to pregnancy and reduced fertility among women previously exposed to PCBs/PCDFs. Because of the limited sample size and the relatively small decrease in fertility rate, these effects should be interpreted with caution.
ENDOCRINE SYSTEM | The PBDE Mixture DE-71 Is Mildly Estrogenic
Polybrominated diphenyl ethers (PBDEs), which are widely found in the environment, may act as endocrine disruptors. Mercado-Feliciano and Bigsby (p. 605) used MCF-7 breast cancer cells and uterotropic bioassays in ovariectomized mice to evaluate the estrogenic activity of the PBDE mixture DE-71. DE-71 behaved as a weak estrogen. However, the authors observed differences in responses between mouse strains (BALB/c mice are more susceptible to DE-71 effects in estrogen target tissues than are C57BL/6 mice) and with various treatment routes and durations of DE-71 exposure. DE-71 increased liver weight, independently of estrogen receptor-α.
CARDIOVASCULAR DISEASE | Long-Term PM10, Metabolic Syndrome, and WBCs
Chen and Schwartz (p. 612) analyzed white blood cell (WBC) count and metabolic syndrome (MS) data from the Third National Health and Nutrition Examination Survey to examine potential inflammatory responses associated with long-term particulate matter (PM) exposure and MS-dependent susceptibility. After adjusting for demographics, socioeconomic factors, lifestyles, residential characteristics, and MS, the researchers observed a statistically significant association between WBC count and estimated local levels of PM10 (PM with aerodynamic diameter < 10 µm). They also found a graded association between PM10 and WBC across subpopulations with increasing MS components.This study revealed a positive association between long-term PM exposure and hematologic markers of inflammation and supported their hypothesis of MS-dependent susceptibility.
NEURODEVELOPMENT | Gestational Lead Exposure and Supernormal Rod ERGs
Postnatal lead exposure in children and animals produces alterations in the visual system primarily characterized by decreases in rod-mediated (scotopic) electroretinogram (ERG) amplitude (subnormality). In contrast, low-level gestational lead exposure (GLE) increases the amplitude of scotopic ERGs in children (supernormality). Fox et al. (p. 618) established a rat model of human equivalent GLE to determine dose–response effects on scotopic ERGs and on retinal morphology, biochemistry, and dopamine metabolism. Low- and moderate-level GLE produced persistent scotopic ERG supernormality due to an increased neurogenesis of cells in the rod signaling pathway and/or decreased dopamine utilization, whereas high-level GLE produced rod-selective toxicity characterized by ERG subnormality.
Also see Science Selections, p. A214
EXPOSURE SCIENCE | Dioxins and Pregnancy Outcomes
Maternal exposure to polychlorinated biphenyls (PCBs) is associated with increased proportions of spontaneous abortion and stillbirth in animal studies. In Japan in 1968, humans were accidentally exposed to rice oil contaminated with PCBs and other dioxin-related compounds, such as polychlorinated dibenzofurans (PCDFs), leading to the development of Yusho oil disease. To investigate the association of maternal PCB and dioxin exposure with adverse pregnancy, Tsukimori et al. (p. 626) interviewed Yusho women about their pregnancy outcomes (spontaneous abortion, preterm delivery, and pregnancy loss) over the past 36 years. Results indicate that high levels of PCB/PCDF exposure had some adverse effects on pregnancy outcome in Yusho women.
CARDIOVASCULAR DISEASE | Particulate Matter and Out-of-Hospital Cardiac Arrest
Particulate matter < 2.5 µm in aerodynamic diameter (PM2.5) is associated with heart disease mortality. Rapid effects of PM2.5 exposure on the cardiovascular system have been proposed, but few studies have investigated the effect of short-term exposures on out-of-hospital cardiac arrest (OHCA). Rosenthal et al. (p. 631) investigated whether short-term PM2.5 exposures increased the risk of OHCA and whether risk depended on subject characteristics or presenting heart rhythm.Results suggest an acute effect of short-term PM2.5 exposure in precipitating OHCAs, but further study is needed to determine the role of various factors that may have increased the risk of cardiovascular disease in the subjects.
SIGNAL TRANSDUCTION | BDE-47 Strongly Affects Ca2+ after Hydroxylation
Oxidative metabolism, resulting in the formation of hydroxylated polybrominated diphenyl ether (PBDE) metabolites, may enhance the neurotoxic potential of brominated flame retardants. Dingemans et al. (p. 637) investigated the effects of a hydroxylated metabolite of 2,2´,4,4´-tetrabromodiphenyl ether (6-OH-BDE-47) on changes in the intracellular Ca2+ concentration and vesicular catecholamine release in PC12 cells. The authors found that the hydroxylated metabolite 6-OH-BDE-47 is more potent in disturbing Ca2+ homeostasis and neurotransmitter release than the parent compound BDE-47. Findings indicate that bioactivation by oxidative metabolism adds considerably to the neurotoxic potential of PBDEs. Also, a cumulative neurotoxic effect of PBDEs and ortho-substituted polychlorinated biphenyls on intracellular Ca2+ concentration cannot be ruled out.
Also see Science Selections, p. A214
IMMUNOLOGY | Immunotoxicity of PFOA
Perfluorooctanoic acid (PFOA), an environmentally persistent compound of regulatory concern, has been reported to reduce antibody responses in mice at a single dose. DeWitt et al. (p. 644) used standard immune function assays in C57BL/6J and C57BL/6N mice to evaluate the effects of PFOA on humoral and cellular immunity. Mice treated with PFOA were immunized with sheep red blood cells or sensitized to bovine serum albumin in Freund's complete adjuvant, and immune responses were determined 1 day after exposure. IgM antibodies were suppressed after PFOA exposure. The margin of exposure for reduced IgM antibody synthesis was approximately 150 for highly exposed human populations.
EXPOSURE SCIENCE | PFC Biomonitoring in Children and Adults
Approximately 40,000 residents of Arnsberg, Germany, were exposed to drinking water contaminated with perfluorinated compounds (PFCs). To assess theinternal exposure of the residents of Arnsberg to six PFCs, compared with reference areas, Hölzer et al. (p. 651) carried out a cross-sectional study on children, mothers, and men. Individual consumption of drinking water and personal characteristics were assessed by questionnaire and interview. PFCs in blood plasma and drinking-water samples were measured by solid-phase extraction, HPLC, and tandem mass spectrometry. PFC concentrations in blood plasma of children and adults exposed to PFC-contaminated drinking water were increased 4- to 8-fold compared with controls.
Children's Health
FETAL DEVELOPMENT | SGA and Preterm Delivery and Prenatal PAH Exposure
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants generated by combustion of organic material, including fossil fuel. Prenatal exposure to air pollution in general and PAHs in particular have been proposed to significantly increase the risk of intrauterine growth restriction, including small size for gestational age (SGA) and preterm delivery. Choi et al. (p. 658) examined this hypothesis in a cohort of mothers and newborns in New York City and found an association between prenatal PAH exposure and the occurrence of SGA as well as preterm births among African Americans. The lack of an association in Dominicans could reflect modification of the risk by healthful cultural practices among recent Dominican immigrants.
Also see Science Selections, p. A215
NEURODEVELOPMENT | Organochlorines and Behavior in Infancy
Several studies have reported an association between organochlorines and behavioral measures in childhood, including inattention. To determine whether prenatal organochlorine exposure is associated with measures of attention in early infancy, Sagiv et al. (p. 666) investigated cord serum concentrations of polychlorinated biphenyls (PCBs) and p,p´-dichlorodiphenyl dichloroethene (DDE) along with measures of attention from the Neonatal Behavioral Assessment Scale (NBAS) in a cohort of 788 infants born during 1993–1998 to mothers residing near a PCB-contaminated harbor and Superfund site in New Bedford, Massachusetts. The authors found evidence for an association between low-level prenatal PCB and DDE exposures and poor attention in early infancy.
Also see Science Selections, p. A215
NEURODEVELOPMENT | Prenatal Exposure to PAHs, Lead, and Mercury and Child Development
Environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), lead, and mercury are released by the combustion of coal and other fossil fuels. Tang et al. (p. 674) evaluated the association between prenatal exposure to these pollutants and child development measured by the Gesell Developmental Schedules at 2 years of age. The study was conducted in Tongliang, Chongqing, China, where a seasonally operated coal-fired power plant was the major source of ambient PAHs and also contributed lead and mercury to the air. The results indicate that exposure to pollutants from the power plant adversely affected the development of children living in Tongliang. These findings have implications for environmental health policy and public health.
FETAL DEVELOPMENT | Traffic Pollution and Birth Outcomes
Evidence suggests that air pollution exposure adversely affects pregnancy outcomes, but few studies have examined individual-level intraurban exposure contrasts. Brauer et al. (p. 680) used spatiotemporal exposure metrics to evaluate the impacts of air pollution on small for gestational age (SGA) birth weight, low full-term birth weight (LBW), and premature birth. Using linked administrative data, the authors identified 70,249 singleton births (1999–2002) with complete covariate data (sex, ethnicity, parity, birth month and year, income, education) and maternal residential history in Vancouver, British Columbia, Canada. In this population-based cohort with relatively low ambient air pollution exposure, associations were observed between traffic-related air pollution and birth outcomes.
EXPOSURE SCIENCE | Pesticide Exposure in Children of Farmworkers
Exposure to organophosphate (OP) pesticides is an occupational hazard for farmworkers, and children can be exposed through the take-home pathway. Thompson et al. (p. 687) examined the effectiveness of a randomized community intervention to reduce pesticide exposure among farmworkers and their children in the Yakima Valley in Washington State. After adjusting for baseline, they found no significant decreases in urinary pesticide metabolite concentrations or in pesticide residue concentrations in house and vehicle dust from intervention-community households compared with control-community households. These negative findings indicate the need for additional research to identify ways to interupt the take-home pathway.
