Evaluating the effectiveness of fish consumption advisories: modeling prenatal, postnatal, and childhood exposures to persistent organic pollutants

Abstract

Background: Because human exposure to persistent organic pollutants (POPs) occurs mainly through ingestion of contaminated food, regulatory bodies issue dietary consumption advisories to describe safe intake levels for food items of concern, particularly fish.

Objectives: Our study goal was to estimate the effectiveness of fish consumption advisories in reducing exposure of infants and children to POPs.

Methods: We used the time-variant mechanistic model CoZMoMAN to estimate and compare prenatal, postnatal, and childhood exposure to polychlorinated biphenyl congener PCB-153 under different scenarios of maternal guideline adherence for both hypothetical constant and realistic time-variant chemical emissions. The scenarios differed in terms of length of compliance (1 vs. 5 years), extent of fish substitution (all vs. half), and replacement diet (uncontaminated produce vs. beef). We also estimated potential exposure reductions for a range of theoretical chemicals to explore how guideline effectiveness varies with a chemical's partitioning and degradation properties.

Results: When assuming realistic time periods of advisory compliance, our findings suggest that temporarily eliminating or reducing maternal fish consumption is largely ineffective in reducing pre- and postnatal exposure to substances with long elimination half-lives in humans, especially during periods of decreasing environmental emissions. Substituting fish with beef may actually result in higher exposure to certain groups of environmental contaminants. On the other hand, advisories may be highly effective in reducing exposure to substances with elimination half-lives in humans shorter than the length of compliance.

Conclusions: Our model estimates suggest that fish consumption advisories are unlikely to be effective in reducing prenatal, postnatal, and childhood exposures to compounds with long elimination half-lives in humans.

Figure 1

Estimated absolute reductions in prenatal, postnatal, and childhood exposure to PCB-153 according to different maternal fish advisory compliance scenarios (relative to no change in fish consumption), and assuming steady-state emissions. Concentration age profiles for each compliance scenario are depicted for 1- and 5-year adherence (A). Exposure profiles are the same for all generations at steady state, and thus the lifetime trends of PCB-153 contamination for a mother and her child under each scenario are depicted on the same graph. Prenatal peak exposure estimated for 1- and 5-year scenarios are depicted as solid bars in (B) and (D), respectively. Postnatal and childhood exposures under 1- and 5-year compliance are displayed in (C) and (E), respectively; the hatched bars represent postnatal exposures, and the solid bars represent childhood exposures. Also, prenatal exposures in (B) and (D) are point estimates of PCB-153 body burden at birth, whereas postnatal and childhood exposures in (C) and (E) are the time-integrated areas under the curve during individuals’ first 6 months and first 9 years of life, respectively.

Figure 2

Estimated percent reductions in prenatal exposure to PCB-153 according to different maternal fish advisory compliance scenarios (relative to no change in fish consumption), and assuming time-variant emissions. The dotted lines represent the percent reduction in prenatal exposure for the same fish consumption scenarios described under steady-state conditions. Plots are overlaid atop the time-variant emissions scenario used in our simulations (Breivik et al. 2010). The same pattern of varying exposure reductions through time was also observed for postnatal PCB-153 exposures (data not shown).

Figure 3

Estimated percent changes in prenatal exposure to perfectly persistent hypothetical chemicals with varying octanol–air (K_oa) and octanol–water partition (K_ow) coefficients at 25°C according to different maternal fish advisory compliance scenarios (relative to no change in fish consumption). Graphs represent the estimated percent change from the calculated default exposure following 5 years of (A) replacing half of fish intake with beef, (B) replacing half of fish intake with produce, (C) replacing all fish intake with beef, and (D) replacing all fish intake with produce, before pregnancy. Perfect persistence assumes no metabolic degradation of the chemical in any modeled organism (including humans); even though no real chemical satisfies this assumption, PCB-153 is shown in each of the plots as a reference. When a reduction in chemical exposure is estimated, the percent change is assigned a negative value (–40 to 0%); when an increase in exposure is estimated, the percent change is positive (0–60%). The area designated by the dashed line indicates the region of enhanced human bioaccumulation potential through the aquatic food chain identified by Undeman et al. (2010).

Figure 4

Estimated percent reductions in prenatal exposure to hypothetical chemicals with varying octanol–air (K_oa) and octanol–water partition (K_ow) coefficients at 25°C according to maternal fish advisory compliance, and assumed human biodegradation half-lives of (A) 1 year, (B) 3 years, (C) 5 years, and (D) 15 years. Graphs represent the estimated percent reduction from the calculated default exposure following 5 years of replacing all fish intake with produce before childbirth. Several POPs are placed in the plots according to their measured partitioning properties and human degradation half-lives. Abbreviations: DDE, dichlorodiphenyldichloroethylene; DDT, dichlorodiphenyltrichloroethane; HpCDD, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin; HpCDF1, 2,3,4,6,7,8-heptachloro-dibenzofuran; HxCDD, 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin; HxCDF, 1,2,3,4,7,8-hexachlorodibenzofuran; OCDD, octachlorodibenzo-p-dioxin; OCDF, octachlorodibenzofuran; PBDE, polybrominated diphenyl ether; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDF, 2,3,7,8-tetrachlorodibenzofuran. (D) Also includes three contaminants with human biodegradation half-lives > 15 years (HxCDD, HpCDD, OCDD). Chemical partitioning properties were identified using data from Åberg et al. (2008), Li et al. (2003), and Schenker et al. (2005), and human degradation half-lives were compiled using data from Geyer et al. (2002, 2004), Milbrath et al. (2009), and Ritter et al. (2009, 2011). When a reduction in chemical exposure is observed, the percent change is assigned a negative value (–100 to 0%). The area designated by the dashed line indicates the region of enhanced human bioaccumulation potential through the aquatic food chain identified by Undeman et al. (2010).