Occurrence of polychlorinated terphenyls (PCTs) in indoor particulate matter

Synthesis of coplanar PCT as reference substances for the residue analysis of polychlorinated terphenyls

In the course of the development of a new and reliable analytical method for the PCT, a group of environmental contaminants, six coplanar terphenyl congeners were synthesized and characterized by means of spectroscopic methods. These congeners are 3,3″,4,4″,5-pentachloro-p-terphenyl, 3,3″,4,5,5″-pentachloro-p-terphenyl, 3,3″,4,5″-tetrachloro-m-terphenyl, 3,3″,4,4″,5-pentachloro-m-terphenyl, 3,3″,5,5',5″-pentachloro-m-terphenyl, and 3,3″,4,4″,5,5″-hexachloro-m-terphenyl. A combination of silica gel column chromatography and preparative NP-HPLC was successfully applied for the first time for the isolation of especially the asymmetrically chlorinated target compounds from product mixtures of the syntheses. For the 29 coplanar, tetra- to heptachlorinated meta- and para-indicator congeners which are envisaged to be used within the analytical method, a simplified systematic nomenclature is suggested. Furthermore, calculation results for all torsion angles of the preferred conformations of the substances are given. The practical relevance of the calculated conformation optima is exemplarily demonstrated by the chromatographic behavior of the PCT compounds.

Polychlorinated biphenyls in residential dust: sources of variability

We characterized the variability in concentrations of polychlorinated biphenyls (PCBs) measured in residential dust. Vacuum cleaner samples were collected from 289 homes in the California Childhood Leukemia Study during two sampling rounds from 2001 to 2010 and 15 PCBs were measured by high resolution gas chromatography-mass spectrometry. Median concentrations of the most abundant PCBs (i.e., PCBs 28, 52, 101, 105, 118, 138, 153, and 180) ranged from 1.0-5.8 ng per g of dust in the first sampling round and from 0.8-3.4 ng/g in the second sampling round. For each of these eight PCBs, we used a random-effects model to apportion total variation into regional variability (6-11%), intraregional between-home variability (27-56%), within-home variability over time (18-52%), and within-sample variability (9-16%). In mixed-effects models, differences in PCB concentrations between homes were explained by home age, with older homes having higher PCB levels. Differences in PCB concentrations within homes were explained by decreasing time trends. Estimated half-lives ranged from 5-18 years, indicating that PCBs are removed very slowly from the indoor environment. Our findings suggest that it may be feasible to use residential dust for retrospective assessment of PCB exposures in studies of children's health.

Determinants of polychlorinated biphenyls in dust from homes in California, USA

Polychlorinated biphenyl (PCB) production ceased in the U.S. over 30 years ago, but these persistent chemicals remain ubiquitous contaminants. Here, we evaluate potential determinants of PCB levels in dust from California homes including characteristics of the residence as well as the residents' habits and occupations. Dust was collected from 415 households as part of a large case-control study (the Northern California Childhood Leukaemia Study), using a high-volume small surface sampler. Dust concentrations of 6 PCBs (PCB-105, PCB-118, PCB-138, PCB-153, PCB-170, and PCB-180) were measured using gas chromatography-mass spectrometry. Individual PCB detection rates ranged from 9% to 54% with PCB concentrations ranging from below detection (1 or 2 ng g (-1)) to 270 ng g(-1) and PCB loadings ranging from below detection to 960 ng m (-2). Multivariable linear and logistic regression models were used to identify potential determinants of residential PCB contamination based on in-home interviews and residential geographic locations. We observed that residences built prior to 1980 had higher odds of PCB detection and higher PCB loadings than more recently constructed homes. Households where residents typically did not remove their shoes had higher PCB dust loadings than households where residents did. PCBs were less likely to be detected in carpet dust from households that had frequently vacuumed or replaced carpets compared to other households. Since we used a cross-sectional dust sampling protocol and report significant, but modest, effects of these determinants on levels of PCBs in residential dust, our results should be interpreted with caution. Longitudinal studies to determine optimal strategies for reducing PCBs in homes are warranted.

Estimating exposures to indoor contaminants using residential dust

Residential dust has been used as a medium for assessing human exposures to a constellation of indoor contaminants including radionuclides, persistent organic pollutants, metals, allergens, and tobacco smoke. Here, we review and comment on investigations of household dust levels of particular analytes of health significance, namely polybrominated diphenyl ethers, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. In doing so, we not only describe methods for collecting and analyzing residential dust, but also describe global patterns in dust levels. Aside from geographic location, we discuss several potential determinants for dust levels of these contaminants. We also review previous estimates of the contribution of dust to overall intake of these three chemical classes and show how residential-dust measurements could be useful in either augmenting or replacing questionnaire-based assessment of human exposures in epidemiological studies. We conclude our review with a discussion of the current gaps in knowledge of worldwide dust levels and suggestions for how residential-dust measurements could be used to describe human exposures to chemicals in developing countries.

Extraction and cleanup methods of dioxins in house dust from two cities in Japan using accelerated solvent extraction and a disposable multi-layer silica-gel cartridge

A simple and rapid method for the extraction and cleanup of dioxins from house dust was developed using an accelerated solvent extraction (ASE) method and a multi-layer silica-gel cartridge. It was found that the WHO-TEQ levels of dioxins extracted from the house dust obtained by both a conventional soxhlet extraction and the ASE were almost equal, when the data obtained by both methods were compared. As for the cleanup method, a multi-layer silica-gel cartridge yielded higher dioxin recoveries than the alkaline digestion method. The average values of the dioxins in house dust from Kumagaya city and Sendai city in Japan (Sendai city is bigger than Kumagaya city with respect to the population and industry), were 15.6 pg TEQ/g (8.6-26.0 pg TEQ/g, n=5, Kumagaya city) and 16.0 pg TEQ/g (5.9-30.5 pg TEQ/g, n=5, Sendai city), respectively.