Storage of serum in plastic and glass containers may alter the serum concentration of polychlorinated biphenyls - Commentary

Environmental Health Perspectives, May, 2004 by Wilfried Karmaus, John F. Riebow

Valid exposure assessment and biomonitoring of toxicants rely on standardized specimen collection, handling, storage, and measurement. In a study designed to determine organochlorine concentrations in blood samples, we recruited participants from registered anglers in Michigan. After participants were interviewed, blood was collected from study subjects, either at home by a phlebotomist or in a commercial blood-draw station. The phlebotomists stored their samples in glass containers, but without our knowledge, the commercial laboratory transferred the specimens to plastic containers for freezing in its central facility. Samples were analyzed in the Analytical Chemistry Section Laboratory of the Michigan Department of Community Health. This laboratory also provided information on storage in glass (n = 28) versus plastic containers (n = 113). We conducted linear regression analyses to assess factors that may explain the concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), and polybrominated biphenyls (PBBs). Our results indicate that storage of serum in plastic containers altered the total concentrations of PCBs, in particular, the higher chlorinated PCBs (PCB-180 and PCB-199), but not DDE or PBBs. No other characteristics of the samples could explain the higher PCB values (0.75 [micro]g/L vs. 0.45 [micro]g/L; p = 0.025) of those stored in plastic containers. The proportion of PCB detects in both subsamples did not differ. Some preceding studies have provided information on whether specimens were stored in glass or plastic containers; however, a number of studies have not. We suggest the initiation of a new review process to determine whether these earlier reports were based on unbiased PCB determinations. We recommend standardizing specimen collection, handling, storage, and measurement, which is particularly necessary for newly emerging analytes. Key words: DDE, glass, PBB, PCB, plastic, storage. Environ Health Perspect 112:643-647 (2004). doi:10.1289/ehp.6768 available via http://dx.doi.org/[Online 2 February 2004]

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Serum concentrations of polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) are frequently used as markers of exposure for different health outcomes including cancer, reproductive failures, and metabolic, endocrine, and developmental disorders (Axmon et al. 2001; Laden et al. 2001; Longnecker et al. 2001; Osius et al. 1999; Walkowiak et al. 2001). Because these compounds are persistent and have long half-lives, single serum or blood measurements are used to assess individual exposure, in 1980, the U.S. Environmental Protection Agency (U.S. EPA) established rules for the collection, preservation, and storage of samples (Watts et al. 1980). These rules were established to minimize the introduction of impurities that might interfere with the quantification of specific analytes by gas chromatography (GC). In particular, plastic containers should be strictly avoided when collecting specimens because of the presence of minute traces of certain components present in plastic that are known to play havoc with GC electron capture detectors. Recently, certain high-density polypropylene containers have become available that may not contaminate samples collected to determine organochlorine compounds (OCs) such as PCBs or DDE (Needham LL, personal communication). Because the U.S. EPA rules established in 1980 have not been updated, environmental studies should adhere to these quality standards. Some studies provide information on whether their study samples were stored in glass containers, as well as how the containers were transported and stored (Longnecker et al. 2000; Nawrot et al. 2002; Walkowiak et al. 2001). However, in a number of publications on OC as markers of exposure, authors omitted information about transportation and storage of samples (e.g., Covaci et al. 2002; Fangstrom et al. 2002; James et al. 2002; Korrick and Altshul 1998; Laden et al. 2001; Moysich et al. 1998; Zheng et al. 2000).

In this article we describe an investigation conducted in Michigan between 1996 and 2000. The objective of the study was to test whether PCB serum concentrations in humans are associated with adverse effect in human reproduction, in particular, male and female hormones. In the course of the study, we learned that commercial blood-draw stations and clinical laboratories stored serum specimens in plastic containers (to the best of our knowledge, high-density polypropylene). Phlebotomists we hired for this study, however, followed the established protocols for the storage of serum specimens in glass containers. In this article, we focus on the question of whether plastic containers may alter the concentration of PCBs, polybrominated biphenyls (PBBs), and DDE in stored serum samples.

Materials and Methods

Population. Participants were recruited from the files of registered anglers in Michigan. According to the established protocols of the Human Subject Committee at Michigan State University, all participants provided written consent. The core study included an interview and collection of blood, either at home by a phlebotomist or in a commercial blood-draw station. Our study design attempted to recruit men and women couples.