Robert G. Lewis

Phase distribution and artifact formation in ambient air sampling for polynuclear aromatic hydrocarbons

Abstract Laboratory and field sampling experiments were conducted to determine the phase-distribution of polynuclear aromatic hydrocarbons (PAH) in the ambient atmosphere and to determine the potential for artifact formation due to volatilization and ozone (O3) reaction during normal sampling conditions. The study was conducted in two segments to investigate both summer and winter ambient temperature effects. The winter measurements reflect stronger association of PAH with the particulate phase than the summer data, but data from both seasons show appreciable filter losses due to volatilization of phenanthrene, anthracene, fluoranthene, benz(a)anthracene and chrysene. No evidence was found for volatilization of the heavier PAH, including benzo(e)pyrene, benzo(a)pyrene, indeno(l,2,3-c,d)pyrene, benzo(g,h,i)perylene and coronene. Although O3 reacted readily with particulate matter that was freshly spiked with PAH in the laboratory experiments, no evidence was found for reaction of O3 with particulate matter during the field sampling experiments.

Monitoring and Reducing Exposure of Infants to Pollutants in House Dust

The health risks to babies from pollutants in house dust may be 100 times greater than for adults. The young ingest more dust and are up to ten times more vulnerable to such exposures. House dust is the main exposure source for infants to allergens, lead, and PBDEs, as well as a major source of exposure to pesticides, PAHs, Gram-negative bacteria, arsenic, cadmium, chromium, phthalates, phenols, and other EDCs, mutagens, and carcinogens. Median or upper percentile concentrations in house dust of lead and several pesticides and PAHs may exceed health-based standards in North America. Early contact with pollutants among the very young is associated with higher rates of chronic illness such as asthma, loss of intelligence, ADHD, and cancer in children and adults. The potential of infants, who live in areas with soil contaminated by automotive and industrial emissions, can be given more protection by improved home cleaning and hand washing. Babies who live in houses built before 1978 have a prospective need for protection against lead exposures; homes built before 1940 have even higher lead exposure risks. The concentration of pollutants in house dust may be 2-32 times higher than that found in the soil near a house. Reducing infant exposures, at this critical time in their development, may reduce lifetime health costs, improve early learning, and increase adult productivity. Some interventions show a very rapid payback. Two large studies provide evidence that home visits to reduce the exposure of children with poorly controlled asthma triggers may return more than 100% on investment in 1 yr in reduced health costs. The tools provided to families during home visits, designed to reduce dust exposures, included vacuum cleaners with dirt finders and HEPA filtration, allergy control bedding covers, high-quality door mats, and HEPA air filters. Infants receive their highest exposure to pollutants in dust at home, where they spend the most time, and where the family has the most mitigation control. Normal vacuum cleaning allows deep dust to build up in carpets where it can be brought to the surface and become airborne as a result of activity on the carpet. Vacuums with dirt finders allow families to use the three-spot test to monitor deep dust, which can reinforce good cleaning habits. Motivated families that receive home visits from trained outreach workers can monitor and reduce dust exposures by 90% or more in 1 wk. The cost of such visits is low considering the reduction of risks achieved. Improved home cleaning is one of the first results observed among families who receive home visits from MHEs and CHWs. We believe that proven intervention methods can reduce the exposure of infants to pollutants in house dust, while recognizing that much remains to be learned about improving the effectiveness of such methods.

Monitoring methods for polycyclic aromatic hydrocarbons and their distribution in house dust and track-in soil

An analytical method was developed and employed to determine polycyclic aromatic hydrocarbons (PAH) in house dust and soil. The method was applied to the analysis of samples collected in an eight-home pilot study that was conducted in Columbus, OH, before and after the 1992/1993 heating season. The purpose of the study was to obtain concentration profiles of PAH in house dust and track-in soil, and to determine whether the track-in of outdoor soil contributes to PAH in house dust. A total of 19 PAH, ranging from naphthalene (2-ring) to coronene (7-ring), were monitored. The sums of concentrations of the 19 PAH ranged from 16 to 580 ppm (w/w) in house dust, from 58 to 5500 ppm in entryway soil, from 0.58 to 1200 ppm in pathway soil, and from 0.63 to 63 ppm in foundation soil. In general, the concentration trend was as follows : entryway soil > house dust > pathway soil > foundation soil. PAH levels in house dust and track-in soil were of the same order of magnitude before and after the heating season. In house dust samples, levels of most 4- to 6-ring PAH, the sums of the 19 PAH, and the sums of the PAH that are probable carcinogens correlated well (r > 0.90 at p < 0.001) with the corresponding levels in the entryway soil samples.

An environmental scoping study in the Lower Rio Grande Valley of Texas — III. Residential microenvironmental monitoring for air, house dust, and soil

A principal aspect of the 1993 Lower Rio Grande Valley Environmental Scoping Study was the analysis and interpretation of residential air, household dust, and soil pollutant concentration data for exposure assessments. Measurements included respirable particulate matter (PM2.5), volatile organic compounds (VOCs), pesticides, and polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air. Household dust, road dust, and yard soil were analyzed for elements, pesticides, and PAHs. Nine residences were monitored for three weeks in the spring of 1993. Additional monitoring was conducted at six of the nine residences for ten days the following summer. Generally good agreement was found between outdoor residential air and same-species measurements collected concurrently at a non-residential central site in Brownsville, TX (Ellenson et al. 1997) for fine particulate matter, elements, and VOCs indicating the dominance of regional influences. PM2.5 mass and element concentrations in residential indoor and outdoor air were generally higher in the summer than in the spring. Indoor air concentrations of many species were higher than outdoor air concentrations and were attributed to household activities, ventilation of residences, and track-in of dislodged soils. Evidence of agricultural activities was noted in the occurrence of crop-related pesticides (e.g., malathion and chlorpyrifos) in indoor and outdoor air. Concentrations of common household pesticides (e.g., chlordane, chlorpyrifos, diazinon, heptachlor, and propoxur) were generally higher indoors than outdoors and were also present in house dust. Seasonal comparisons of pesticides and PAHs were also presented using matched residences in spring and summer; VOCs also may have indicated seasonal effects. VOCs (notably propane and butane isomers) and PAHs were higher indoors, presumably due to cooking-related activities.

Design and performance of a high-volume compound annular denuder

Abstract A laminar flow model incorporating variable collisional reaction efficiency is developed and applied for the design of annular denuders. Efficiencies predicted with the model show excellent agreement with published empirical data for annular denuders that are used for collection of SO 2 , but point to potential errors in extending the empirical data to different chemical systems. The design and construction of a compound annular denuder for collection of polynuclear aromatic hydrocarbon (PAH) vapor are described. This denuder, which consists of a nested set of cylindrical tubes, is shown to operate efficiently at sampling rates of up to 3.33 l s −1 while maintaining essentially 100 per cent transmission of micron-sized particulate matter.

Experimental methodologies and preliminary transfer factor data for estimation of dermal exposures to particles

Developmental efforts and experimental data that focused on quantifying the transfer of particles on a mass basis from indoor surfaces to human skin are described. Methods that utilized a common fluorescein-tagged Arizona Test Dust (ATD) as a possible surrogate for housedust and a uniform surface dust deposition chamber to permit estimation of particle mass transfer for selected dust size fractions were developed. Particle transfers to both wet and dry skin were quantified for contact events with stainless steel, vinyl, and carpeted surfaces that had been pre-loaded with the tagged test dust. To better understand the representativeness of the test dust, a large housedust sample was collected and analyzed for particle size distribution by mass and several metals (Pb, Mn, Cd, Cr, and Ni). The real housedust sample was found to have multimodal size distributions (mg/g) for particle-phase metals. The fluorescein tagging provided surface coatings of 0.11–0.36 ng fluorescein per gram of dust. The predominant surface location of the fluorescein tag would best represent simulated mass transfers for contaminant species coating the surfaces of the particles. The computer-controlled surface deposition chamber provided acceptably uniform surface coatings with known particle loadings on the contact test panels. Significant findings for the dermal transfer factor data were: (a) only about 1/3 of the projected hand surface typically came in contact with the smooth test surfaces during a press; (b) the fraction of particles transferred to the skin decreased as the surface roughness increased, with carpeting transfer coefficients averaging only 1/10 those of stainless steel; (c) hand dampness significantly increased the particle mass transfer; (d) consecutive presses decreased the particle transfer by a factor of 3 as the skin surface became loaded, requiring ∼100 presses to reach an equilibrium transfer rate; and (e) an increase in metals concentration with decreasing particle size, with levels at 25 μm typically two or more times higher than those at 100 μm — consistent with the earlier finding of Lewis et al. for the same sample for pesticides and polycyclic aromatic hydrocarbons (PAHs).

Measurement of atmospheric concentrations of common household pesticides: A pilot study.

Air concentrations of 28 of the most commonly used household pesticides were measured inside nine homes in Jacksonville, Florida, and compared with corresponding outdoor levels. The households selected were sorted into three categories according to the degree of pesticide indoor usage. Personal air monitoring was also performed on one resident of each household by means of a portable sampler, which was kept with the person at all times. Five of the pesticides were found in the air inside of the majority of the homes at concentrations as high as 15 μgm−3 (average concentrations, 12 ngm−3 to 2.4 μgm−3). Indoor levels were generally one to two ordrrs of magnitude higher than surrounding outdoor air levels and personal air measurements were within ± 50% of corresponding indoor values. All samples were collected over 24-hr periods on polyurethane foam and analyzed by capillary colum gas chromatography with mass spectrometric and/or electron capture detection.

Efficiency of silicone-grease-coated denuders for collection of polynuclear aromatic hydrocarbons

Abstract The overall efficiency of silicone-grease-coated denuders was determined for the collection of selected 3- and 4-ring polynuclear aromatic hydrocarbons (PAH). PAH studied were fluorene, phenanthrene, anthracene, acenaphthene and pyrene. Fluorene was subsequently eliminated from consideration because of analytical problems caused by the reactivity of this compound. Results are interpreted in terms of the collisional reaction efficiencies (γ) for these compounds. An analysis of the effects of uncertainties in diffusion coefficients and γ values for these compounds on overall phase distributions derived from experimental data suggests that the consequences of these uncertainties are less significant than normal variations due to sampling and analysis effects.

THE ENVIRONMENTAL PROTECTION AGENCY'S RESEARCH PROGRAM ON TOTAL HUMAN EXPOSURE

Abstract The U.S. Environmental Protection Agencys (U.S. EPA) research program on total human exposure to environmental pollution seeks to develop a newly emerging concept in the environmental sciences. Instead of focusing purely on the sources of pollution or their transport and movement through the environment, this research focuses on human beings as the receptors of these pollutants. People and daily activities become the center of attention. The methodology measures and models the pollutant concentrations found at the physical boundaries of people, regardless of whether the pollutants arrive through the air, water, food, or skin. It seeks to characterize quantitatively the impact of pollution on people by determining if an environmental problem exists at the human interface and, if so, by determining the sources, nature, extent, and severity of this environmental problem. By exploiting an emerging new arsenal of miniaturized instruments and by developing statistically representative survey designs for sampling the population of cities, significant progress has been made in recent years in providing previously unavailable human exposure field data needed for making valid risk assessments. The U.S. EPA total human exposure research program includes: development of measurement methods and instruments, development of exposure models and statistical protocols, microenvironmental field studies, total human exposure studies, validation of human exposure models with empirical data, and dosage research investigations.

An environmental scoping study in the lower Rio Grande Valley of Texas : I. Comparative assessment of air sampling methods

Abstract The atmospheric monitoring component of the 1993 Lower Rio Grande Valley Environmental Scoping Study measured a wide range of pollutant species from different sampling and analysis methods. Extensive QA/QC activities were also conducted on the sampling and analysis techniques. This enabled a unique comparison of these methods to provide insights into air sampling for larger, long-term exposure monitoring studies. Pollutants monitored were particulate mass and elements, acidic gases, volatile organic compounds, pesticides, and polycyclic aromatic hydrocarbons. This included collocated monitoring devices which monitored same-species pollutants. Sample collection efficiencies of certain atmospheric pollutants are discussed. Finally, data from two sites located in the Lower Rio Grande Valley are also presented and compared.