Environews
FOCUS | In Hot Water: Global Warming Takes a Toll on Coral Reefs
With the increased frequency and severity of hurricanes, tornadoes, and other extreme weather conditions, it would appear few populations are remaining unscathed. One population suffering the harsh effects of climate change is corals. Record high temperatures in marine waters have caused the bleaching of large numbers of coral reefs across the globe, leading to the widespread deterioration of a resource that provides food and storm protection for millions of people. This article (p. A292) examines the danger posed by global warming to coral reefs through bleaching and susceptibility to disease, and looks at the best current thinking regarding potential protective treatments.
SPHERES OF INFLUENCE | Ozone Nation: EPA Standard Panned by the People
Ozone and its associated pollutants are linked to premature death, upper and lower respiratory diseases such as asthma and bronchitis, heart attacks, and other cardiovascular problems, with effects noted at levels as low as 10 ppb. As the Environmental Protection Agency prepared to set a new standard for ground-level ozone, the prevailing recommendation was for somewhere between 60 and 70 ppb. When the standard was set at 75 ppb in March 2008, few—if any—stakeholders were pleased. This article (p. A302) takes a look at how the new standard was set, what it means for counties across the United States, and why it has been so sharply criticized.
Review
ASTHMA | Phthalates, Asthma, and Allergies
Phthalates from polyvinyl chloride (PVC) plastics may have adverse effects on airways and immunologic systems, but the evidence has not been reviewed systematically. Jaakkola and Knight (p. 845) reviewed the evidence for the role of exposure to phthalates from PVC products in the development of asthma and allergies. Data from from 27 human and 14 laboratory toxicology studies indicated that high levels of phthalates can modulate the murine immune response to a coallergen. Heated PVC fumes may contribute to development of asthma in adults, and epidemiologic studies in children show associations between indicators of phthalate exposure in the home and risk of asthma and allergies. Epidemiologic data are limited by the lack of objective exposure information.
Research
TOXICOLOGY | Antioxidants Prevent Cd-Induced Ototoxicity
Several heavy metals have been shown to have toxic effects on the peripheral and central auditory system. Given the current rate of release of cadmium (Cd2+) into the environment, the amount of Cd2+ present in the human body and the incidence of Cd2+-related diseases are expected to increase. Kim et al. (p. 854) examinedthe mechanism of Cd2+-induced ototoxicity in cultured HEI-OC1 cells, organ of Corti explants, and mouse cochlea. They found that reactive oxygen species generation may be the cause of the toxicity and that application of antioxidants, such as N-acetyl-l-cysteine, can prevent the toxic effect.
NANOTECHNOLOGY | Preventing Airborne Nanoparticle Exposure
Airborne nanoparticles from vehicle emissions have been associated with adverse effects in people with pulmonary and cardiovascular disease, and toxicologic studies have shown that nanoparticles can be more hazardous than their larger-scale counterparts. Recirculating air filtration in automobiles and houses may provide a low-cost solution to reducing exposures in many cases, thus reducing possible health risks. Pui et al. (p. 863) investigated the effectiveness of recirculating air filtration on reducing exposure to incidental and intentionally produced airborne nanoparticles under two scenarios: while driving in traffic, and while generating nanomaterials using gas-phase synthesis.
REPRODUCTIVE HEALTH | UV Filters and Fetal Prostate Development
Many environmental endocrine disruptors have been shown to exhibit disruption of normal cellular and developmental processes in animal models. Ultraviolet (UV) filters used as sunscreens in cosmetics have previously been shown to exhibit estrogenic activity in in vitro and in vivo assays. Hofkamp et al. (p. 867) examined the effects of two UV filters, 4-methylbenzylidene camphor (4-MBC) and 3-benzylidene camphor, in the prostate of developing male rats and found that 4-MBC during development of the accessory sex glands exhibited classical growth effects associated with estrogenic endocrine disruptors. The different regional responses suggest that the developmental processes of ductal outgrowth and branching morphogenesis are affected independently by exposure to these environmental chemicals.
GENE REGULATION | Arsenic Induces NRF2-Mediated K16 Gene Expression
Inorganic sodium arsenite (iAs), a ubiquitous environmental contaminant, is associated with an increased risk of skin hyperkeratosis and cancer. Endo et al. (p. 873) investigated the molecular mechanisms underlying the regulation of the keratin 16 (K16) gene by iAs in the HaCaT human keratinocyte cell line. The data indicate that the K16 gene is a novel target of NRF2. The findings also suggest that NRF2 has opposing roles in the cell—in the activation of detoxification pathways and in promoting the development of skin disorders.
GENE REGULATION | Interspecies Variation in SXR
Nuclear receptor subfamily 1, group I, member 2 (NR1I2), commonly known as steroid and xenobiotic receptor (SXR) in humans, is a key ligand-dependent transcription factor responsible for the regulation of xenobiotic, steroid, and bile acid metabolism. The ligand-binding domain is principally responsible for species-specific activation of NR1I2 in response to xenobiotic exposure. Milnes et al. (p. 880) screened a variety of xenobiotic compounds for interaction with NR1I2 orthologs within a common system to provide the framework for understanding the metabolism of xenobiotic compounds in different model species. They evaluated their results in light of using these species to predict xenobiotic disposition and assess environmental health risk.
BREAST CANCER | PBPK Modeling for Lifetime POP Exposure Assessment
Despite experimental evidence, most epidemiologic studies to date have not supported an association between exposure to persistent organic pollutants (POPs) and breast cancer incidence in humans. Verner et al. (p. 886) developed a tool to estimate lifetime blood/tissue exposure and levels of POPs during any hypothesized time window of susceptibility in breast cancer development. The new lifetime physiologically based pharmacokinetic (PBPK) model shows the limitations of using a single sample value obtained around the time of diagnosis for lifetime exposure assessment, and enables researchers to reduce uncertainty linked to past POPs exposure estimation and to consider exposure during time windows that are hypothesized to be mechanistically critical in carcinogenesis.
Also see Science Selections, p. A307
BIOMONITORS | Exposure Assessment of the U.S. Population to Benzophenone-3
The capability of benzophenone-3 (BP-3) to absorb and dissipate ultraviolet (UV) radiation facilitates its use as a sunscreen agent. BP-3 also has other uses in consumer products (e.g., fragrance and flavor enhancer, photoinitiator, UV curing agent, polymerization inhibitor). Calafat et al. (p. 893) assessed exposure to BP-3 in a representative sample of the U.S. general population GREATEQ 6 years of age. They detected BP-3 in 96.8% of the samples; exposure to BP-3 was prevalent in the general U.S. population during 2003–2004. Differences by sex and race/ethnicity probably reflect differences in use of personal care products containing BP-3.
Also see Science Selections, p. A306
CARDIOVASCULAR DISEASE | Biomarkers of Systemic Inflammation and Air Pollution
Biomarkers of systemic inflammation have been associated with risk of cardiovascular morbidity and mortality. To clarify associations of particulate matter (PM) air pollution with systemic inflammation, Delfino et al. (p. 898) used models based on size-fractionated PM mass and markers of primary and secondary aerosols. The authors followed a panel of 29 nonsmoking elderly subjects, all with a history of coronary artery disease (CAD), living in retirement communities in the Los Angeles, California, air basin. Results suggest that traffic emission sources of primary organic carbon and quasi-ultrafine particles lead to increased systemic inflammation and platelet activation and decreased antioxidant enzyme activity in elderly people with CAD.
EXPOSURE SCIENCE | Exposure to Indoor Air Pollution in Urban and Rural China
Biomass fuel is the primary source of domestic fuel in much of rural China; however, previous studies have not characterized particle exposure through time–activity diaries or personal monitoring in mainland China. Jiang and Bell (p. 907) characterized indoor and personal particle exposure in six households in northeastern China and explored differences by location, cooking status, activity, and fuel type. Rural homes used biomass, and urban homes used a combination of electricity and natural gas. The findings indicate that biomass burning for cooking contributes substantially to indoor particulate levels and that this exposure is particularly elevated for cooks.
NANOTECHNOLOGY | Quantum Dots Elevate Cytoplasmic Ca2+ and Impair Voltage-Gated Sodium Channels
The growing applications of nanotechnologic products, such as quantum dots (QDs), increase the likelihood of exposure. Furthermore, their accumulation in the bioenvironment and retention in cells and tissues are causing increasing worries about the potentially harmful side effects of these nanotechnologic products. Previous studies concerning QD cytotoxicity focused on the reactive oxygen species produced by QDs. Tang et al. (p. 915) investigated the potential for neurotoxicity of cadmium selenium QDs in a hippocampal neuronal culture model, focusing on cytoplasmic calcium levels and voltage-gated sodium channel function. Results from this study provide new insights into QD toxicology and reveal potential risks of their future applications in biology and medicine.
REPRODUCTIVE HEALTH | Endocrine Disruptor–Induced Prostatitis
Androgens are critical for specifying prostate development, with the fetal prostate sensitive to altered hormone levels and endocrine-disrupting chemicals (EDCs) that exhibit estrogenic or antiandrogenic properties. Prostatic inflammation (prostatitis) affects 9% of men of all ages, and > 90% of cases are of unknown etiology. Cowin et al. (p. 923) evaluated the effects of in utero exposure to the antiandrogenic EDC vinclozolin during the period of male reproductive tract development. Prostate histology remained normal until puberty, but 100% of animals displayed prostatitis postpubertally. The data are the first to unequivocally implicate EDCs as a causative factor and fill an important knowledge gap on the etiology of prostatitis.
METABOLISM | Brevetoxin–Nucleic Acid Adduction in Rat Lung
Human exposure to brevetoxins produced by the red tide organism, Karenia brevis, is an increasing public health concern. A previous study using in vitro exposure of rat liver cells to brevetoxin B (PbTx-2), the primary toxin product of K. brevis, showed that PbTx-2 formed C27,28-epoxy brevetoxin metabolites capable of covalently binding to nucleic acids, a common initiation step for carcinogenesis. Radwan and Ramsdell (p. 930) evaluated nucleic acid adduction in lung following in vitro and in vivo brevetoxin exposures and found that PbTx-2 forms DNA adducts with cytidine after treatment of isolated lung cells and DNA adducts with adenosine and guanosine after intratracheal exposure. The results are consistent with metabolic activation of highly reactive brevetoxin intermediates that bind to nucleic acid.
CARDIOVASCULAR DISEASE | Vascular Effects of Diesel Exhaust
Traffic-related air pollution is consistently associated with cardiovascular morbidity and mortality, and recent human and animal studies suggest that exposure to air pollutants affects vascular function. Peretz et al. (p. 937) examined the effects of short-term exposure to diesel exhaust (DE), a major source of traffic-related air pollution, on vascular reactivity and on mediators of vascular tone. Results show that short-term exposure to DE is associated with acute endothelial response and vasoconstriction of a conductance artery. The signaling pathways controlling vascular tone require further elucidation.
NEURODEGENERATIVE DISEASE | Lead Exposure and ALS Survival
Kamel et al. (p. 943) determined whether lead exposure, assessed by measuring blood and bone lead levels, is associated with survival in amyotrophic lateral sclerosis (ALS). Reasons for the variability in survival among ALS cases are unknown but may include exposure to environmental neurotoxicants. The authors evaluated the relationship of lead exposure to ALS survival in 110 cases from a case–control study conducted in New England (USA) in 1993–1996 that included measurements of blood and bone lead. Results suggest that lead exposure is associated with longer survival in ALS cases and, if confirmed, may shed light on mechanisms involved in disease progression.
ENDOCRINE SYSTEM | Measuring Endocrine-Sensitive Endpoints in Early Life
Arbuckle et al. (p. 948) report on the international workshop "Assessing Endocrine-Related Endpoints within the First Years of Life." Representatives from a number of pregnancy cohort studies in North America and Europe presented options for measuring various endocrine-sensitive endpoints in early life and discussed issues related to performing and using those measures. The workshop focused on measuring reproductive tract developmental endpoints, such as anogenital distance, endocrine status, and infant anthropometry.
Environmental Medicine
RISK CHARACTERIZATION | Arsenic and Pterygium
Pterygium is a fibrovascular growth of the bulbar conjunctiva and underlying subconjunctival tissue that may cause blindness. Pterygium also has some tumorlike features, such as abnormal p53 expression and uncontrolled cell proliferation. To evaluate the association between arsenic exposure through drinking water and the occurrence of pterygium, Lin (p. 952) conducted a study in southwestern Taiwan in which participants from an arseniasis-endemic area in southwestern Taiwan and from neighboring nonendemic villages each received an eye examination and a questionnaire interview. The authors found a significant association between cumulative arsenic exposure and the prevalence of pterygium. After adjusting for exposures to sunlight and sandy environments, arsenic remained an independent predictor for pterygium.
Children's Health
NEUROBEHAVIORAL DISEASE | Environmental Toxicants and Conduct Disorder
Braun et al. (p. 956) examined the association of tobacco smoke and environmental lead exposure with conduct disorder (CD). The National Health and Nutrition Examination Survey 2001–2004 (NHANES) is a nationally representative cross-sectional sample of the noninstitutionalized U.S. population. The study examined the association of prenatal tobacco, postnatal tobacco, and environmental lead exposure with CD in children 8–15 years of age. Parents completed the Diagnostic Interview Schedule for Children to determine whether their children met criteria of the Diagnostic and Statistical Manual of Mental Disorders for CD. The results suggest that prenatal tobacco exposure and environmental lead exposure contribute substantially to CD in U.S. children.
Also see Science Selections, p. A307
EXPOSURE SCIENCE | Infant Arsenic Exposure via Breast Milk
Chronic arsenic exposure causes a wide range of health effects, but little is known about critical windows of exposure. Arsenic readily crosses the placenta, but the few available data on postnatal exposure to arsenic via breast milk are not conclusive. Fängström et al. (p. 963) assessed the arsenic exposure through breast milk in Bangladeshi infants, living in an area with high prevalence of arsenic-rich tube-well water. Very little arsenic is excreted in breast milk, even in women with high exposure from drinking water. Thus, exclusive breast-feeding protects the infant from exposure to arsenic.
Also see Science Selections, p. A306
ASTHMA | Traffic-Related Air Pollution, Stress, and Asthma
Chen et al. (p. 970) examined how physical and social environments combine to affect asthma. Along with interviews with both children and parents, diaries of symptoms, and measurements of peak expiratory flow rate (PEFR), they assessed traffic-related air pollution with a land use regression model for nitrogen dioxide concentrations. NO2 interacted with stress, parent-reported symptoms, and PEFR, indicating that chronic higher levels of stress can exacerbate asthma symptoms.
PUBERTY | Blood Lead Levels and Onset of Puberty in Boys
Epidemiologic studies showing earlier onset and longer duration of puberty suggest the influence of environmental factors. Hauser et al. (p. 976) used regression models to examine the relationship of blood lead levels and the onset of puberty in Russian boys 8–9 years of age, based on testicular volume (TV) and pubertal staging. Height, weight, body mass index, birth weight, and gestational age were predictive of the onset of puberty as, assessed either by TV (> 3 mL), genitalia stage or both. The findings indicate that relatively low blood lead levels (GREATEQ5 µg/dL) were associated with decreased growth and differences in pubertal onset in periadolescent Russian boys.
RISK ASSESSMENT | Reduction of Elevated Blood Lead Levels in Children
Few studies have examined factors related to the time required for children's BLLs GREATEQ 10 µg/dL to decline to < 10 µg/dL. Dignam et al. (p. 981) used routinely collected surveillance data to determine the length of time and risk factors associated with reducing elevated blood lead levels (BLLs) in children below the level of concern of 10 µg/dL. Children with high confirmatory BLLs, black children, males, and children from rural areas may need additional attention during case management to expedite their BLL reduction time to < 10 µg/dL.