PCB-containing wood floor finish is a likely source of elevated PCBs in residents' blood, household air and dust: a case study of exposure.

BACKGROUND: Polychlorinated biphenyls (PCBs) are persistent pollutants identified worldwide as human blood and breast milk contaminants. Because they bioaccumulate, consumption of meat, fish, and dairy products predicts human blood concentrations. PCBs were also used widely in building materials, including caulks and paints, but few studies have evaluated the contribution of these exposures to body burden.
METHODS: In an earlier study, we detected PCBs in indoor air in 31% of 120 homes on Cape Cod, MA. Two of the homes had much higher concentrations than the rest, so we retested to verify the initial finding, evaluate blood PCB concentrations of residents, and identify the PCB source.
RESULTS: Air and dust concentrations remained elevated over 5 years between initial and follow-up sampling. Blood serum concentrations of PCBs in residents of the homes were generally elevated above the 95th percentile of a representative sample of the US population. Serum concentrations in residents and air and dust concentrations were especially high in a home where a resident reported use of PCB-containing floor finish in the past, and where the floor of one room was sanded and refinished just prior to sample collection.
CONCLUSION: This case-study suggests that PCB residues in homes may be more significant contributors to overall exposure than diet for some people, and that use of a commercially-available PCB-containing wood floor finish in residences during the 1950s and 1960s is an overlooked but potentially important source of current PCB exposure in the general population.

Background

Polychlorinated biphenyls (PCBs) are persistent organic pollutants and have been identified worldwide as human blood and breast milk contaminants. They are established developmental neurotoxicants in humans [1,2], with elevated prenatal PCB concentrations being associated with cognitive deficits in children [1,3-5]. PCBs are also associated with thyroid toxicity, effects on immune, reproductive, nervous, and endocrine systems, and cancer effects including breast cancer [6-10].

PCBs were primarily used in electrical equipment and fluorescent lighting fixtures prior to 1977, but can also be found in other products manufactured before 1977 such as plasticizers, surface coatings, inks, adhesives, flame retardants, pesticide extenders, carbonless duplicating paper, paints, wire insulators, caulking materials, elastic sealants, and heat insulation [6]. Because of the tendency of PCBs to bioaccumulate, several studies have concluded that consumption of meat and dairy products, as well as processed foods and fish, contributes significantly to overall intake of PCBs [11-15].

It is likely that major contributors to PCB exposure vary across the population depending on proximity to specific sources. For example, studies of Great Lakes fish eaters have shown that fish consumption is a significant predictor of blood PCB concentrations [16,17]. Use of PCB-contaminated caulk in commercial buildings and schools, which appears to be common in pre-1980 construction [18,19], has been shown to increase blood PCB concentrations, especially for lower-chlorinated congeners [20,21]. A few studies have proposed that multiple pathways contribute significantly to total human PCB exposure. Currado and Harrad determined that inhalation could account for 6 to 64% (mean 25%) of overall human PCB exposure [22].

In 2003 we reported results from a household exposure study of 120 homes on Cape Cod [23]. We tested for 89 target chemicals, mostly endocrine disrupting compounds (EDCs), and detected 52 chemicals in air and 66 in dust. Three PCB congeners were among the target chemicals: PCB 52, PCB 105, and PCB 153. We detected PCBs in air (>1 ng/m3) from 38 homes (32%) and dust (>0.2 μg/g) from 22 homes (18%) [23]. PCBs were detected in air in 76% of homes where it was detected in dust. Two homes had much higher air and dust PCB concentrations (sum of PCB 52, 105, 153 in air 23 and 35 ng/m3; dust 21 and 68 μg/g) than the rest of the study sample (max of sum PCB 52, 105, 153 in air 14 ng/m3; median < 3 ng/m3; max in dust 8 μg/g, median < 0.6 μg/g). These two homes were retested in an attempt to verify the initial finding, evaluate blood PCB concentrations of residents, and identify the source of PCBs with an ultimate goal of recommending potential exposure reduction techniques to the homeowners.

Methods

Human research review committees at Brown University, Providence, RI, and at the Shattuck Hospital, Boston, MA, approved study protocols and all participants provided informed consent prior to sampling.

The 120 participants of the Cape Cod household exposure study were female breast cancer cases or age-matched controls who had participated in the case-control portion of the Cape Cod Breast Cancer and Environment Study [24] and had lived in their home at least 10 years at the time of original sampling (1999–2001). The average age of the women in the exposure study was 75 (median 77). In 2004–2005, new air and dust samples were collected from the 2 homes with high PCBs, and a visual survey of each house and the general area around the 2 homes was conducted to identify any potential sources of PCBs (e.g., electrical or industrial equipment, fluorescent lights, industrial window sealant, etc.). Residents were also asked about electrical and mechanical hobbies, businesses, historical land use, flooring, lighting, and older electrical equipment.

Sampling took place in single-family owner-occupied homes on Cape Cod, Massachusetts. Cape Cod is a coastal peninsula consisting of 15 towns in Southeastern Massachusetts. The area has very little industry and is considered a summer vacation destination. Follow-up air and dust samples were collected in winter 2004–2005, 4–6 years after the initial samples were taken from these homes, and analyzed using the same methods reported previously [23,25]. Briefly, air samples were collected over 24 hours by drawing air at 8–9 L/min through a personal pesticide sampling cartridge (University Research Glassware, URG). URG cartridges were fitted with a quartz fiber filter followed by XAD-2 resin sandwiched between two polyurethane foam (PUF) plugs. The total volume of air sampled ranged from 10–14 cubic meters.

Dust samples were collected using a Eureka Mighty-Mite vacuum cleaner, modified to collect dust through a Teflon crevice tool into a cellulose extraction thimble (Whatman Inc., Clifton, NJ). Dust sample collection did not begin until the air sample collection was complete. Sample collection was accomplished by slowly and lightly drawing the crevice tool just above the surface of rugs, upholstery, wood floors, windowsills, ceiling fans and furniture in each room. Sampling was conducted in the most frequently-used rooms of the house, usually 4–5 rooms and including hallways. Cellulose thimbles containing dust were placed in cleaned glass sample jars with Teflon lined lids (Environmental Sampling Supply, Oakland, CA). URGs and dust samples were stored at -4°C until they were shipped overnight on dry ice to Southwest Research Institute (SWRI) for analysis. Prior to extraction, dust was tapped out of the thimbles, weighed, and sieved to < 150 microns.

Chemical analysis of air and dust samples was conducted at SWRI, San Antonio, TX as described in [23,25]. Each XAD-2/PUF/filter was soxhlet extracted in 6% ether in hexane. Each sieved (< 150 um) dust sample was spiked with surrogate, equilibrated, then soxhlet extracted using 6% ether in hexane. The extracts were concentrated and cleaned by running through a florisil column. Analysis was performed using an Agilent 6890/5973 GC/MS in selected ion monitoring (SIM) mode. The GC/MS instrument was scanned to monitor the following ions: PCB 52 (290,294), PCB 105 (324,328), PCB 153 (362,358). The base peak ion was used as the quantification ion for each compound. Quantification was performed using d12-labeled PAHs as internal standards. PCBs were not detected in air matrix blanks or dust extraction blanks. Congener sums assumed a value of 0 for values below the detection limit.

Within one month of air and dust re-sampling, blood samples were collected from residents of the two homes with elevated PCBs to better describe personal exposure. Serum samples were analyzed for 33 PCB congeners along with several other organochlorines (e.g., p,p'-dichlorodiphenyl dichloroethylene, or 4,4'-DDE) at the Environmental Chemistry Laboratory, Division of Analytical Chemistry, Massachusetts Department of Public Health State Laboratory Institute in Jamaica Plain, MA. The analysis followed the AOAC standard method for polychlorinated biphenyls in serum [26] and involved extraction with hexane/ethyl ether, silica column cleanup with hexane elution, and analysis by dual column gas chromatography with electron capture detection as described in Brock et al. [27]. Standard operating procedures for all analyses are available from the authors. Results were reported as ng/g lipid and detection limits were about 15 ng/g lipid. Any detects in a reagent blank prepared and analyzed with the samples were subtracted from sample results. Congener sums assumed a value of 0 for below detection limit values. These sums underestimate total PCB concentrations in serum because 1) zero very likely underestimates the concentrations of some congeners that may be present below detection limits, and 2) only 33 of 209 PCB congeners were analyzed.

Results

PCBs in Indoor Air

PCBs in indoor air remained elevated on re-testing in both homes with high PCB concentrations in the initial study (Table 1). Measurements were taken in the living area of the homes initially, and in the living area and bedroom at retest. In home #1, living area concentrations remained high. PCBs were not detected in the bedroom, which was on the second floor of the home, but the limit of detection was elevated because of the small sample volume (see Table 1). Home #2 was small and the living area and bedroom were close together – concentrations were similar in both rooms. Both retest samples were collected during the winter, while initial samples from home 1 were collected in winter and home 2 in summer.

Table 1

PCB concentrations in indoor air, house dust, and residents' serum in two Cape Cod homes

		Indoor air(ng/m3)a		House dust (micrograms/gram)a		Serum (ng/g lipid)
Home	Participant	Initial PCBs, LR [52,105,153]	Follow-up PCBs LR (BR) [52,105,153]	Initial PCBs [52, 105, 153]	Follow-up PCBs [52, 105, 153]	Total PCBs (# congeners detected)b	Sum 10 PCB congenersc	4,4'-DDEd
1	1-A	23 [19, 4, <2]	21 (<68) [10, 2.9, 7.7]	21 [1.1, 14, 5.8]	190 [15, 53, 119]	1630 (13)	1520	848
	1-Be					993 (11)	967	208
2	2-A	35 [25, 6.7, 3.6]	8.0 (13) [8, <2.8, <2.8]	68 [16, 35, 17]	140 [37, 34, 69]	760 (16)	652	292
	2-B					179 (5)	179	96

Abbreviations: PCB, polychlorinated biphenyl; LR, living room; BR, bedroom; ND, not detected; DL, detection limit

aPCB concentrations reported as sum of PCB 52, 105, 153 in air or dust (

bSum of the concentrations of all PCB congeners detected in serum (of 33 tested). Values < DL set to 0. Individual congeners reported in Additional File 1

cLimited to the 10 PCB congeners also measured in NHANES. Values < DL set to 0

dIncluded as an alternate bioaccumulative, persistent organochlorine

aPCB concentrations reported as sum of PCB 52, 105, 153 in air or dust (