IMPLICATIONSSemi-volatile organic and inorganic compounds can represent a substantial fraction of ambient particulate mass. Loss of semi-volatile compounds during filter collection can occur due to changes in the composition of the air sample. Heating of the air sample to a temperature 10-20 °C above ambient to remove particle-bound water can further enhance loss of the semi-volatile constituents of ambient particles. These losses depend on particle composition, which varies with location and time. Thus, it is not possible to determine the true concentration by using empirical factors to correct the observed concentrations. Therefore, to minimize losses of semi-volatile compounds, we recommend that particle mass measurements be made at temperatures comparable to ambient. In urban areas, a substantial fraction of ambient PM can be semi-volatile material. A larger fraction of this component of PM 10 may be lost from the TEOM-heated filter than the Federal Reference Method (FRM). The observed relationship between TEOM and FRM methods varied widely among sites and seasons. In East Coast urban areas during the summer, the methods were highly correlated with good agreement. In the winter, correlation was somewhat lower, with TEOM PM concentrations generally lower than the FRM. Rubidoux, CA, and two Mexican sites (Tlalnepantla and Merced) had the highest levels of PM 10 and the largest difference between TEOM and manual methods.PM 2.5 data from collocation of 24-hour manual samples with the TEOM are also presented. As most of the semi-volatile PM is in the fine fraction, differences between these methods are larger for PM 2.5 than for PM 10 .

A modeling study was conducted to examine the distribution of concentrations of the antimicrobial triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) in rivers following discharge from wastewater treatment plants (WWTPs). Most uses of triclosan are disposed of down residential drains and ultimately reach WWTPs. A modeling analysis was conducted to simulate the discharge of triclosan in WWTP effluents to rivers and calculate the expected concentrations based on characteristics of the reach where the discharge occurred, the estimated concentration of triclosan in the WWTP effluent, and the physicochemical properties of triclosan. A probabilistic exposure assessment was conducted based on data on the characteristics of U.S. reaches receiving wastewater discharges and the physicochemical characteristics of triclosan. A risk assessment was conducted by comparing the estimated concentrations with toxicity endpoint concentrations for species representative of key ecological groups. For fish and invertebrates, neither acute nor chronic risks are of concern, and no concerns exist for vascular aquatic plants. However, certain types of algae are the most sensitive species to triclosan by more than an order of magnitude than other algal or aquatic plant species. For these algae, the potential exists for some risk from triclosan exposure near the WWTP discharge location during low-flow-rate periods for some WWTPs with small dilutions. The risks downstream are lower because of dissipation of triclosan.

Ambient particulate matter (PM) is a complex mixture of inorganic and organic compounds. The U.S. Environmental Protection Agency (EPA) regulates PM as a criteria pollutant and promulgates National Ambient Air Quality Standards for it. The PM indicator is based on mass concentration, unspecified as to chemical composition, for specific size fractions. The numerical standards are based on epidemiologic evidence of associations between the various size-related particle mass concentrations as indicators and excess mortality and cardiorespiratory health effects as endpoints. The U.S. National Research Council has stated that more research is needed to differentiate the apparent health effects associated with different particle chemical constituents. Sulfate and nitrate constitute a significant portion of the particle mass in the atmosphere, but are accompanied by similar amounts of carbonaceous material, along with low concentrations of various species, including bioactive organic compounds and redox cycling metals. Extensive animal and human toxicology data show no significant effects for particles consisting only of sulfate and nitrate compounds at levels in excess of ambient air concentrations. A few epidemiologic studies, including both short-term time-series studies and long-term cohort studies, have included the sulfate content of PM as a specific variable in health effect analyses. There are much less data for nitrate. The results from the epidemiologic studies with PM sulfate are inconsistent. A detailed analysis of the time-series epidemiological studies shows that PM sulfate has a weaker "risk factor" than PM2.5 for health effects. Since sulfate is correlated with PM2.5, this result is inconsistent with sulfate having a strong health influence. However, there are many limitations with these types of studies that warrant caution for any comparison between a chemical component and mass concentration. In total, the epidemiologic and toxicologic evidence provide little or no support for a causal association of PM sulfate and health risk at ambient concentrations. For nitrate-containing PM, virtually no epidemiological data exist. Limited toxicological evidence does not support a causal association between particulate nitrate compounds and excess health risks. There are some possible indirect processes through which sulfate and nitrate in PM may affect health-related endpoints, including interactions with certain metal species and a linkage with production of secondary organic matter. There is insufficient evidence to include or exclude these processes as being potentially important to PM-associated health risk.

Triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) is a broad-spectrum bactericide used throughout North America and Europe for a variety of antimicrobial functions. This paper addresses the risk to terrestrial organisms from several potential exposure pathways: Exposure experienced by earthworms, terrestrial plants, and soil microorganisms as the result of the use of sewage sludge containing triclosan as an agricultural soil amendment; secondary exposure by birds and mammals from consumption of earthworms that have been exposed to triclosan in soil; and secondary exposure by birds and mammals from consumption of fish exposed to triclosan as the result of wastewater treatment discharges. The assessment found satisfactory margins of safety for plants, earthworms, birds, fish, mammals, and soil microorganisms. The lowest margins of safety were for nontarget plants (100 for the typical scenario and 8 for the upper-bound scenario). However, these margins of safety are still above the European Union (EU) recommended fivefold assessment value for nontarget plants and are based on cucumber results from a vegetative vigor study conducted in quartz sand that is of limited relevance for risk assessment. In a pre-emergence study conducted in a more relevant soil (sandy loam), cucumbers showed no response to triclosan at the highest dose tested (1,000 microg/kg). A recent study provides limited field measurements of soil and earthworm concentrations. While that study finds higher soil and earthworm concentrations than were estimated in the present study, even these higher concentrations do not indicate significant risks.

The heterogeneous chemistry of ozone on interior latex paint was investigated in a tube flow reactor. The emissions of several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured while a glass tube coated with latex paint was exposed to clean air and ozone. Four different commercial brands of latex paint were tested. Formic and acetic acids were notfound to be generated via ozone reactions; however, both were found to off-gas from the latex paints, and the off-gasing increased with increasing relative humidity. The off-gasing rates are large enough, particularly for acetic acid, to impact residential concentrations significantly. Formaldehyde was found to be produced by reactions related to the ozone concentration. There was some evidence that acetaldehyde and acetone may also be produced by processes related to the ozone concentration. A steadystate model is presented that is used to extrapolate the chamber results to a representative indoor environment. The model is based on an experimentally derived parameter termed the VOC formation factor, which is defined as the number of VOC molecules of a particular species formed via an ozone reaction divided by the total number of ozone molecules sticking to the surface. Using this model, it was found that formaldehyde production via ozone reactions is significant enough to impact indoor concentrations of formaldehyde.