Species-specific concentrations of perfluoroalkyl contaminants in farm and pet animals in Japan

Abstract

The persistent metabolites of perfluorinated compounds (PFCs) which have been detected in the tissues of both humans and wildlife, and human contamination by PFCs suggest differences in the exposure patterns to these compounds. However, studies focused on identifying human exposure pathways to PFCs are scarce. To provide a preliminary assessment of PFCs in farm animals such as chicken, cattle, pigs, goats and horses, blood and liver samples were collected from various regions in Japan. Additionally, dog sera samples representing pet animals were also employed for analysis. Perfluorooctane sulfonate (PFOS) was the most prominent contaminant found in farm and pet animals, with mean sera PFOS concentrations (in decreasing order) of: chicken (5.8 ng/ml) > cattle (3.0 ng/ml) > goat (2.4 ng/ml) > horse (0.71 ng/ml) > pig (0.37 ng/ml). Chicken livers (67 ng/g) contained the highest mean PFOS concentration among the farm animals, followed by those of pigs (54 ng/g) and cattle (34 ng/g). In comparison to PFOS levels in farm animals, the detected levels of other PFCs were not significant. The high levels of PFOS found in cattle fetal livers suggest that PFOS crosses the placental barrier to enter fetal circulation. The consumption of chicken by humans might produce higher PFOS exposure in humans compared to that in farm animals; however, the current levels of PFOS in farm animals in Japan were lower than those reported in fish and wild animals. Elevated concentrations of both PFOS (25 ng/ml) and perfluorohexane sulfonate (PFHxS; 10 ng/ml) were found in dog sera, indicating that further studies are needed to identify PFC sources in the human environment.

Introduction

Perfluorinated compounds (PFCs), which have a wide range of industrial and consumer applications, have been used for over 50 years. The strong carbon–fluorine (C–F) covalent bonds present in PFCs account for the thermal and chemical stability of these compounds, which thus resist hydrolysis, photolysis, biodegradation and metabolism (Kissa, 2001). It has been reported that PFCs are found in several species of wildlife and fish from various locations, including remote areas (Kannan et al., 2001a, Kannan et al., 2001b, Kannan et al., 2002). These compounds bind to serum albumin and are found in the protein fraction of blood (Han et al., 2003). Some studies have reported the occurrence of PFCs in the body fluids of non-occupationally exposed humans in various geographical locations (Olsen et al., 2003a, Olsen et al., 2003b, Kannan et al., 2004, Guruge et al., 2005a). Potentially serious health effects of certain PFCs have been reported, including liver damage and detrimental effects on development, thyroid and pancreatic functions and reproduction and even mortality in animals (Seacat et al., 2002, Thibodeaux et al., 2003, Kennedy et al., 2004, Lau et al., 2004). Therefore, the occurrence of these chemicals in the human body has raised considerable public health concerns about the effects of these chemicals. Since these compounds are found in various concentrations in humans, it is important to focus on pathways of exposure. Human exposure to organochlorine pollutants through foodstuffs originating from animals, for example, is considered to be greater than exposure through other pathways. Therefore, monitoring PFCs in domestic animals will provide insight not only into animal contamination, but also into potential human exposure through ingestion of animal products. PFC contamination in edible fish, wild animals and drinking water has been reported worldwide, however, data are scarce for farm animals. In the present study, the concentrations of several PFCs in the sera, plasma and livers of six species of farm and pet animals were measured to determine current contamination levels in animals from several locations in Japan.