An alternative form and level of the human health ozone standard.

Controlled human laboratory studies have shown that there is a disproportionately greater pulmonary function response from higher hourly average ozone (O3) concentrations than from lower hourly average values and thus, a nonlinear relationship exists between O3 dose and pulmonary function (FEV1) response. The nonlinear dose-response relationship affects the efficacy of the current 8-h O3 standard to describe adequately the observed spirometric response to typical diurnal O3 exposure patterns. We have reanalyzed data from five controlled human response to O3 health laboratory experiments as reported by Hazucha et al.

Real-time PCR-based prediction of gonad phenotype in medaka.

An important endpoint in aquatic bioassays for potential endocrine disrupting chemicals (EDCs) is the gonadal phenotype of exposed fish, with special interest in intersex and sex-reversed individuals. Traditionally, the assessment of gonad phenotype is done via histology, which involves specialized and time-consuming techniques. The method detailed here increases the efficiency of the analysis by first determining the relative expression of four genes involved in gonad development/maintenance in Japanese medaka (Oryzias latipes), and then by using principal component analysis, assigning a phenotype to each gonad based upon the gene expression data.

Spatial variability of PM2.5 in urban areas in the United States.

Data from the U.S. Environmental Protection Agency's Aerometric Information Retrieval System (now known as the Air Quality System) database for 1999 and 2000 have been used to characterize the spatial variability of concentrations of particulate matter with aerodynamic diameter < or = 2.

Techniques to assess cross-border air pollution and application to a US-Mexico border region.

A year-long assessment of cross-border air pollution was conducted in the eastmost section of the US-Mexico border region, known as the Lower Rio Grande Valley, in South Texas. Measurements were conducted on the US side and included fine particle mass (PM2.5) and elemental composition, volatile organic compounds (VOCs) and meteorology.

Changes in diurnal patterns related to changes in ozone levels.

Ozone is an ubiquitous air pollutant that affects both human health and vegetation. There is concern about the number of hours human populations in nonattainment areas in the United States are exposed to levels of O3 at which effects have been observed. As improvement in air quality is achieved, it is possible that O3 control strategies may produce distributions of 1-h O3 concentrations that result in different diurnal profiles that produce greater potential exposures to O3 at known effects levels for multiple hours of the day.

The characterization of ozone concentrations at a select set of high-elevation sites in the eastern United States.

Hourly averaged data for ozone collected in 1986 and 1987 were analyzed and characterized for a select set of high-elevation sites in the eastern United States. Pressure-corrected adjustments may be necessary when comparing ozone concentrations measured at two different elevations. When unadjusted concentrations (i.