Trends of VOC exposures among a nationally representative sample: Analysis of the NHANES 1988 through 2004 data sets

Abstract

Exposures to volatile organic compounds (VOCs) are ubiquitous due to emissions from personal, commercial and industrial products, but quantitative and representative information regarding long term exposure trends is lacking. This study characterizes trends from1988 to 2004 for the 15 VOCs measured in blood in five cohorts of the National Health and Nutrition Examination Survey (NHANES), a large and representative sample of U.S. adults. Trends were evaluated at various percentiles using linear quantile regression (QR) models, which were adjusted for solvent-related occupations and cotinine levels. Most VOCs showed decreasing trends at all quantiles, e.g., median exposures declined by 2.5 (m, p-xylene) to 6.4 (tetrachloroethene) percent per year over the 15 year period. Trends varied by VOC and quantile, and were grouped into three patterns: similar decreases at all quantiles (including benzene, toluene); most rapid decreases at upper quantiles (ethylbenzene, m, p-xylene, o-xylene, styrene, chloroform, tetrachloroethene); and fastest declines at central quantiles (1,4-dichlorobenzene). These patterns reflect changes in exposure sources, e.g., upper-percentile exposures may result mostly from occupational exposure, while lower percentile exposures arise from general environmental sources. Both VOC emissions aggregated at the national level and VOC concentrations measured in ambient air also have declined substantially over the study period and are supportive of the exposure trends, although the NHANES data suggest the importance of indoor sources and personal activities on VOC exposures. While piecewise QR models suggest that exposures of several VOCs decreased little or any during the 1990’s, followed by more rapid decreases from 1999 to 2004, questions are raised concerning the reliability of VOC data in several of the NHANES cohorts and its applicability as an exposure indicator, as demonstrated by the modest correlation between VOC levels in blood and personal air collected in the 1999/2000 cohort. Despite some limitations, the NHANES data provides a unique, long term and direct measurement of VOC exposures and trends.

Extreme value analyses of VOC exposures and risks: A comparison of RIOPA and NHANES datasets

“…In contrast, RIOPA used in-home measurements, and thus common staging and the associated trips were not required. Staging may have affected both the level and variability of NHANES data and caused other differences, e.g., we have noted discrepancies in some of the NHANES blood VOC data in earlier cohorts and the surprisingly low correlation between VOC levels in blood and personal air (Su et al, 2011). …”

“…In NHANES, occupations dealing with services, precision production, craft and repair, operators, fabricators, and laborers, totaled 40% of the sample (Su et al, 2011); these occupations were judged to have potential for VOC exposure. Narrower job definitions were possible in RIOPA.…”

Levels and sources of volatile organic compounds in homes of children with asthma

“…Concentrations of VOCs measured in different studies can differ for many reasons. Levels in more recent studies (after 2000 or so) are often lower due to progress made in controlling indoor and outdoor emissions, as well as the reduction or elimination in indoor smoking (Batterman et al., ; McCarthy et al., ; Su et al., ). Because outdoor VOC levels provide a ‘floor’, indoor concentrations can be affected by urbanization, proximity to industry, traffic and other emission sources, and meteorology.…”

Evaluation of potential health effects associated with occupational and environmental exposure to styrene – an update

“…Evaluating trends in cotinine-adjusted NHANES data from 1988vs. 1990, Su, Mukherjee, and Batterman (2011 observed no significant decrease in styrene concentrations in blood per year. However, annual reductions of 8.2-12.3% (depending on the quantile) occurred between data sets.…”