Assessing health risks from multiple environmental stressors: Moving from G×E to I×E.

Research on disease causation often attempts to isolate the effects of individual factors, including individual genes or environmental factors. This reductionist approach has generated many discoveries, but misses important interactive and cumulative effects that may help explain the broad range of variability in disease occurrence observed across studies and individuals. A disease rarely results from a single factor, and instead results from a broader combination of factors, characterized here as intrinsic (I) and extrinsic (E) factors.

Association between Exposure to '-DDT and Its Metabolite '-DDE with Obesity: Integrated Systematic Review and Meta-Analysis.

Background: The prevalence of obesity is increasing in all countries, becoming a substantial public health concern worldwide. Increasing evidence has associated obesity with persistent pollutants such as the pesticide DDT and its metabolite '-DDE.

Objectives: Our objective was to systematically review the literature on the association between exposure to the pesticide DDT and its metabolites and obesity to develop hazard identification conclusions.

Active smoking and secondhand smoke increase breast cancer risk: the report of the Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk (2009).

Four authoritative reviews of active smoking and breast cancer have been published since 2000, but only one considered data after 2002 and conclusions varied. Three reviews of secondhand smoke (SHS) and breast cancer (2004-2006) each came to different conclusions. With 30 new studies since 2002, further review was deemed desirable.

Inhalation of an essential metal: development of reference exposure levels for manganese.

Exposures to high levels of manganese by ingestion or inhalation can damage the central nervous system. However, the capacity of environmental manganese to cause neurotoxicity is of most concern following inhalation exposure. Reference exposure levels (RELs) are values developed by California EPA's Office of Environmental Health Hazard Assessment (OEHHA) to protect the general public from periodic and continual exposures to airborne toxicants.

Development of TEFs for PCB congeners by using an alternative biomarker--thyroid hormone levels.

Polychlorinated biphenyls (PCBs) are ubiquitous toxic contaminants. Health risk assessment for this class of chemicals is complex: the current toxic equivalency factor (TEF) method covers dioxin-like (DL-) PCBs, dibenzofurans, and dioxins, but excludes non-DL-PCBs. To address this deficiency, we evaluated published data for several PCB congeners to determine common biomarkers of effect.

Do standard risk assessment procedures adequately account for cumulative risks?: an exploration of the possibilities using California's Air Toxics Hot Spots guidelines.

Existing risk assessment data and procedures can be used to address the estimation of cumulative risk, but there are several uncertainties. These are explored in the context of the State of California's Air Toxic Hot Spots program. Hazard identification for single agents is an established procedure but is much more complex for incompletely characterized or variable mixtures.

Potential new approaches for children's inhalation risk assessment.

The U.S. Environmental Protection Agency (EPA) practice of risk assessment is moving toward more thoroughly considering children's unique susceptibilities and exposure potential.

Focusing on children's inhalation dosimetry and health effects for risk assessment: an introduction.

Substantial effort has been invested in improving children's health risk assessment in recent years. However, the body of scientific evidence in support of children's health assessment is constantly advancing, indicating the need for continual updating of risk assessment methods. Children's inhalation dosimetry and child-specific adverse health effects are of particular concern for risk assessment.

Evaluation and application of the RD50 for determining acceptable exposure levels of airborne sensory irritants for the general public.

Background: The RD(50) (exposure concentration producing a 50% respiratory rate decrease) test evaluates airborne chemicals for sensory irritation and has become an American Society for Testing and Materials (ASTM) standard method. Past studies reported good correlations (R(2)) between RD(50)s and the occupational exposure limits, particularly threshold limit values (TLVs).

Objective: The main purpose of this study was to examine the relationship between RD(50)s and human sensory irritation responses in a quantitative manner, particularly for chemicals that produce burning sensation of the eyes, nose, or throat, based on lowest observed adverse effect levels (LOAELs) reported for human subjects.

The association between exposure to environmental tobacco smoke and breast cancer: a review by the California Environmental Protection Agency.

Background: The California Environmental Protection Agency (Cal/EPA) recently completed a health effects assessment of exposure to environmental tobacco smoke (ETS) which resulted in California listing ETS as a Toxic Air Contaminant in January 2006. As part of the assessment, studies on the association between exposure to ETS and breast cancer were reviewed.

Methods: Twenty-six published reports (including 3 meta-analyses) evaluating the association between ETS exposure and breast cancer were reviewed.

Development of a chronic inhalation reference level for respirable crystalline silica.

Chronic inhalation exposure of workers to crystalline silica can result in silicosis. The general public can also be exposed to lower levels of crystalline silica from quarries, sand blasting, and entrained fines particles from surface soil. We have derived an inhalation chronic reference exposure level for silica, a level below which no adverse effects due to prolonged exposure would be expected in the general public.

Acute toxicity and cancer risk assessment values for tert-butyl acetate.

tert-Butyl acetate (TBAc) is an industrial chemical with potential uses as a degreaser and in architectural coatings. Limited chronic toxicity data exist for TBAc. However, acute inhalation exposure data are available for TBAc.