Search

Diesel exhaust (DE) contains a variety of toxic air pollutants, including diesel particulate matter (DPM) and gaseous contaminants (e.g., carbon monoxide (CO)). DPM is dominated by fine (PM2.5) and ultrafine particles (UFP), and can be representatively determined by its thermal-optical refractory as elemental carbon (EC) or light-absorbing characteristics as black carbon (BC). The currently accepted reference method for sampling and analysis of occupational exposure to DPM is the National Institute for Occupational Safety and Health (NIOSH) Method 5040. However, this method cannot provide in-situ short-term measurements of DPM. Thus, real-time monitors are gaining attention to better examine DE exposures in occupational settings. However, real-time monitors are subject to changing environmental conditions. Field measurements have reported interferences in optical sensors and subsequent real-time readings, under conditions of high humidity and abrupt temperature changes. To begin dealing with these issues, we completed a controlled study to evaluate five real-time monitors: Airtec real-time DPM/EC Monitor, TSI SidePak Personal Aerosol Monitor AM510 (PM2.5), TSI Condensation Particle Counter 3007, microAeth AE51 BC Aethalometer, and Langan T15n CO Measurer. Tests were conducted under different temperatures (55, 70, and 80°F), relative humidity (10, 40, and 80%), and DPM concentrations (50 and 200 μg/m3) in a controlled exposure facility. The 2-hr averaged EC measurements from the Airtec instrument showed relatively good agreement with NIOSH Method 5040 (R2= 0.84; slope = 1.17±0.06; N = 27) and reported ∼17% higher EC concentrations than the NIOSH reference method. Temperature, relative humidity, and DPM levels did not significantly affect relative differences in 2-hr averaged EC concentrations obtained by the Airtec instrument vs. the NIOSH method (p < 0.05). Multiple linear regression analyses, based on 1-min averaged data, suggested combined effects of up to 5% from relative humidity and temperature on real-time measurements. The overall deviations of these real-time monitors from the NIOSH method results were ≤20%. However, simultaneous monitoring of temperature and relative humidity is recommended in field investigations to understand and correct for environmental impacts on real-time monitoring data. [ABSTRACT FROM PUBLISHER]

Georgopoulos and Lioy (1994) presented a theoretical framework for exposure analysis, incorporating multiple levels of empirical and mechanistic information while characterizing/reducing uncertainties. The present review summarizes efforts towards implementing that framework, through the development of a mechanistic source-to-dose Modeling ENvironment for TOtal Risks studies (MENTOR), a computational toolbox that provides various modeling and data analysis tools to facilitate assessment of cumulative and aggregate (multipathway) exposures to contaminant mixtures.MENTOR adopts a “Person Oriented Modeling” (POM) approach that can be applied to either specific individuals or to populations/subpopulations of interest; the latter is accomplished by defining samples of “virtual” individuals that statistically reproduce the physiological, demographic, etc., attributes of the populations studied. MENTOR implementations currently incorporate and expand USEPA's SHEDS (Stochastic Human Exposure and Dose Simulation) approach and consider multiple exposure routes (inhalation, food, drinking water intake; non-dietary ingestion; dermal absorption). Typically, simulations involve: (1) characterizing background levels of contaminants by combining model predictions and measurement studies; (2) characterizing multimedia levels and temporal profiles of contaminants in various residential and occupational microenvironments; (3) selecting sample populations that statistically reproduce essential demographics (age, gender, race, occupation, education) of relevant population units (e.g., census tracts); (4) developing activity event sequences for each member of the sample by matching attributes to entries of USEPA's Consolidated Human Activity Database (CHAD); (5) calculating intake rates for the sample population members, reflecting physiological attributes and activities pursued; (6) combining intake rates from multiple routes to assess exposures; (7) estimating target tissue doses with physiologically based dosimetry/toxicokinetic modeling. [ABSTRACT FROM AUTHOR]

Studies five methods of sampling lead-contaminated dust on carpets and compared in homes of children with elevated blood lead levels in New Jersey. Wipe method; Adhesive label method; Sheet method; Vacuum method; Hand rinse method.

The adhesion of house dust particles and chemical residues to the hands after contact with a variety of surfaces can yield significant exposures to children. Chemicals present on the surface or absorbed into house dust particles may adhere to the hands and subsequently are available for ingestion or absorption through the skin under normal physiological conditions. Contact of a hand with a surface occurs primarily through a thin layer of sebum and sweat on the skin surface. The study presented here examined the effect of the composition of the sebum and sweat layer on the adhesion of a mixture of pesticides and a herbicide to a hand after contact with a house-dust-laden surface. Collection efficiencies on the hand for atrazine and malathion were correlated with sebum levels on the palm of an individual hand. The increase in sebum values measured in this study caused a 13 percent and 8 percent reduction in collection efficiency, respectively, for atrazine and malathion applied to house-dust-laden surfaces. Diazinon and chlorpyrifos collection efficiencies were correlated with skin hydration levels measured on the palm of the individual's hand. The increased skin hydration measured in this study caused a 7 percent and 5 percent reduction in collection efficiency, respectively, for diazinon and chlorpyrifos. [ABSTRACT FROM AUTHOR]

ABSTRACT. During the winter of 1988-1989, parents of 2,789 elementary-school students completed standardized questionnaires. The students were 5-14 y of age and were from three urban districts and one suburban district of three large Chinese cities. The 4-y average ambient levels of total suspended particles in the three cities differed greatly during the period 1985-1988: Lanzhou, 1,067 Mu g/m[sup 3]; urban Wuhan, 406 Mu g/m[sup 3]; Guangzhou, 296 Mu g/m[sup 3]; and suburban Wuhan, 191 Mu g/m[sup 3]. The authors constructed unconditional logistic-regression models to calculate odds ratios and 95% confidence intervals for prevalences of several respiratory symptoms and illnesses, adjusted for district, use of coal in the home, and parental smoking status. There was a positive and significant association between total suspended particle levels and the adjusted odds ratios for cough, phlegm, hospitalization for diseases, and pneumonia. This association was derived from only the 1,784 urban children and, therefore, the authors were unable to extrapolate it to the suburban children. The results also indicated that parental smoking status was associated with cough and phlegm, and use of coal in the home was associated only with cough prevalence (a = 0.05). [ABSTRACT FROM AUTHOR]

Studies methods of toxicology exposure analysis and assessment in the 21st century. Multidisciplinary science issues covered by the exposure assessment; Changing concepts and view of the field by the scientific community; Exposure measurement and modeling.

As a result of the 1975 Moodus Conference, a task force was established to analyze the ozone data from the 19 Moodus states and to assess the importance of ozone transport across the Midwestern and Northeastern United States. Data from daily ozone maps, aerial ozone measurements, and trajectory analysis are used in this paper to describe the typical summertime ozone episode in the Moodus study area. The results indicate that ozone concentrations in a high pressure system as it moves out of Canada into the Midwest are typically 30–50 ppb. Higher concentrations first develop over the areas of high anthropogenic percursor emissions. As the high pressure moves eastward, the areas of high ozone increase in size and concentration and eventually merge together. Verticle ozone profiles conducted on consecutive days and nights suggest an ozone half‐life of 46.8 h above the nocturnal inversion layer. Using the corresponding dark phase rate of ozone decay in conjunction with air parcel trajectories, it was estimated that, under certain conditions, over 100 ppb of ozone are transported from the Midwest to the Northeastern Atlantic Coast. [ABSTRACT FROM PUBLISHER]

Investigates the efficacy of breath ammonia depletion methods in acid aerosol exposure-health response studies in Piscataway, New Jersey. Use of a nitrogen oxides analyzer; Reduction of exhaled ammonia; Need for repeated oral rinsing to maintain low-breath ammonia conditions.