Polybrominated diphenyl ethers in fish and wastewater samples from an area of the Penobscot River in Central Maine

Abstract

Polybrominated diphenyl ethers (PBDEs) are one class of flame retardants commonly used in textiles, foams and plastics. They are similar in behavior to the well-studied polychlorinated biphenyls and growing evidence suggests they are widespread global environmental pollutants that are capable of bioaccumulation. Fish tissue samples were collected from sites along the Penobscot River in central Maine. The total concentration of tetra- to hepta-PBDEs in these samples were calculated and generally increased from upstream to downstream locations ranging from 800 to 1810 ng/g lipid at the northernmost site to 5750–29 000 ng/g at the downstream sampling site. BDE-47, 99 and 100 were the predominant congeners found in the fish tissue. Wastewater treatment plants (WWTPs) are one of the potential sources of these compounds to the environment through effluent discharge and landspreading of biosolids. Influent, effluent, activated sludge and dewatered biosolids were collected and analyzed for PBDE congeners from a WWTP at Orono, Maine. PBDE congeners were detectable in effluent samples at concentrations from 0.31 to 0.90 μg/l, in the activated sludge at 1.32–3.8 μg/l and in the influent at 4.2–4.3 μg/l, but the majority of the material was concentrated in the biosolids. Total concentration in the biosolids was 2320–3530 μg/kg dry weight.

Introduction

Brominated flame retardants (BFRs) are used in an increasingly broad range of products and materials. The majority of BFRs are of the additive type, meaning that they are simply blended with, not covalently bound to, materials. Polybrominated diphenyl ethers (PBDEs) are the second highest production group of BFRs currently in use. The structure of PBDE is similar to polychlorinated biphenyls (PCBs), and the same nomenclature system is used for the 209 possible congeners (Ballschmiter and Zell, 1980). There are three major commercial mixtures of these compounds: the penta-, octa- and deca-mixes. Penta-BDE, marketed under the trade names Bromkal-70 and DE-71, contains predominately the congeners BDE-47, 99, 100, 153, and 154. It is used predominately in polyurethane foams and textiles. The octa mix, which is principally composed of BDE-183 and 153, is used in styrenes, polycarbonates and thermosets. Deca mixtures are used in most types of synthetic materials including textiles and electronics (Alcock et al., 2003, Birnbaum and Staskal, 2004).

In recent years, concerns have been rising about the global presence of BFRs in all levels of ecosystems. Their tendency for atmospheric transport results in a moderate potential for global redistribution (Gouin et al., 2002, Uneo et al., 2004). In contrast to declining levels of PCBs, dioxins and DDT in the environment over the last 20 years, levels of BFRs have increased in North America (Luross et al., 2000, Ikonomou et al., 2002, Stern and Ikonomou, 2000) and studies have indicated current levels could adversely affect sensitive human populations, such as young children, indigenous peoples and fish consumers (de Wit, 2002). These compounds are highly lipophilic and readily bioaccumulate in the food chain in a manner similar to dioxins and PCBs (de Wit, 2002). Exposure to PBDEs has been shown to affect motor skills and learning as well as thyroid hormone metabolism (MacDonald, 2002). Rodent studies show that PBDEs have the potential to disrupt thyroid hormone transport and may act as endocrine disruptors (Legler and Brouwer, 2003).

Humans are exposed to PBDEs through consumption of foods of animal origin, inhalation of contaminated particles or direct contact with materials that have been treated with flame retardants (Vos et al., 2003). Dust and air have both been shown to have measurable PBDE concentrations and inhalation could account for up to one quarter of total exposure (Harrad et al., 2004). Ambient air concentrations range from 5 to 300 pg/m³ with the higher values taken in urban areas. Recent studies by Rudel et al. (2003) have shown that concentrations of a selected group of PBDE congeners in household dust ranged from 0.7 to 4.1 μg/g dust. Hites (2004) reported values as high as 1800 pg/m³ and Wilford et al. (2004) reported that even when the ambient air concentration was less than 5 pg/m³, median indoor values were 120 pg/m³ with the highest value being 3600 pg/m³.

The transport and fate of PBDEs is not completely understood. Potential routes to the environment include the disposal of material containing BFRs in landfills, discharge from wastewater treatment plants (WWTPs) and industrial sources, land application, incineration or volatilization into the atmosphere (Hale et al., 2003). Wastewater treatment plants represent a known source of PBDEs. Previous studies by Nylund et al. (1992) and Oberg et al. (2002) surveyed concentrations of BFRs in WWTPs in Sweden and found that the penta formulation congeners were present in the biosolids and the concentration varied with local sources. Other studies have also indicated that PBDE congeners are present in WWTP effluent (De Boer et al., 2003, North, 2004).

Preliminary data (Anderson, unpublished data, 2001) indicated the presence of PBDEs in several species of fresh water fish in the Penobscot River. The purpose of this study was to determine which congeners are present and begin assessing potential sources of BFRs in the watershed. We measured PBDEs at various points in a wastewater treatment plant which discharges to the river and in fish obtained above and below the outfall to determine what congeners are present and if WWTPs might represent important sources of contamination.