Intestinal absorption and biomagnification of organic contaminants in fish, wildlife, and humans

Abstract

Methods for the regulatory assessment of the bioaccumulation potential of organic chemicals are founded on empirical measurements and mechanistic models of dietary absorption and biomagnification. This study includes a review of the current state of knowledge regarding mechanisms and models of intestinal absorption and biomagnification of organic chemicals in organisms of aquatic and terrestrial food chains and also includes a discussion of the implications of these models for assessing the bioaccumulation potential of organic chemicals. Four mechanistic models, including biomass conversion, digestion or gastrointestinal magnification, micelle-mediated diffusion, and fat-flush diffusion, are evaluated. The models contain many similarities and represent an evolution in understanding of chemical bioaccumulation processes. An important difference between the biomagnification models is whether intestinal absorption of an ingested contaminant occurs solely via passive molecular diffusion through serial resistances or via facilitated diffusion that incorporates an additional advective transport mechanism in parallel (i.e., molecular ferrying within gastrointestinal micelles). This difference has an effect on the selection of physicochemical properties that best anticipate the bioaccumulative potential of commercial chemicals in aquatic and terrestrial food chains. Current regulatory initiatives utilizing Kow threshold criteria to assess chemical bioaccumulation potential are shown to be unable to identify certain bioaccumulative substances in air-breathing animals. We urge further research on dietary absorption and biomagnification of organic chemicals to develop better models for assessing the bioaccumulative nature of organic chemicals.

Maternal transfer of organohalogenated compounds in sharks and stingrays

“…Biomagnification is a major pathway for several persistent organic pollutants (POPs) and is a frequent factor in biomonitoring studies (Kelly et al, 2004(Kelly et al, , 2008Johnson-Restrepo et al, 2005;Burreau et al, 2006;Ikonomou and Addison, 2008). Additive to biomagnification, there is also the further potential of direct pollutant transfer from parent to offspring.…”

Mathematical relationships between metrics of chemical bioaccumulation in fish

“…It has units of m 3 food/m 3 water. This ratio is fairly constant for most chemicals, but it can be smaller for hydrophobic chemicals of log K OW exceeding 7 that have lower dietary assimilation efficiencies [21][22][23]. The food-water concentration ratio, C D /C W , is the BAF of the prey, and it can vary greatly in magnitude and has units of m 3 water/m 3 food.…”

“…An implication is that organisms with high food intake and lipid absorption efficiencies approaching 100% will experience high BMFs. Homeotherms such as mammals and birds are obvious examples [23].…”

“…If growth, biotransformation, or fecal egestion is significant, the BCF K is less than K FW , implying that although steady state is reached, true equilibrium is not achieved. Second, a BAF may correspond to an increase in fugacity because the fish absorbs chemical from the food, which experiences a decrease in lipid content during digestion and hence a decreasing Z value and a corresponding increase in fugacity [23]. If monitored aquatic species show an increase in fugacity or lipid-normalized concentration with trophic level, this indicates significant biomagnification as distinct from simple bioconcentration.…”

A P450 gene associated with robust resistance to DDT in ciliated protozoan, Tetrahymena thermophila by efficient degradation

“…The half-life of DDT is 0.25-15 years in soils, and more than four years in humans (Longnecker, 2005;van den Berg, 2009). DDT can accumulate in organisms by bioaccumulation and biomagnification through the food chain and, being highly lipophilic, can integrate with lipids in a stable state (Kelly et al, 2004). Therefore, DDT remains a significant threat to wildlife and human health.…”