Guidance for measuring and evaluating biomagnification factors and trophic magnification factors of difficult substances: application to decabromodiphenylethane

Abstract

As field based trophic magnification factors (TMFs) and biomagnification factors (BMFs) become more prominent regulatory metrics used in bioaccumulation assessments of commercial chemicals, there is a need to develop standardized guidelines for conducting field-based bioaccumulation studies and to establish methods using weight of evidence analyses of those studies. Hence, the primary objectives of this study were (1) to compile a set of comprehensive criteria and guidelines for conducting field-based biomagnification studies and (2) to develop a weight of evidence meta-analysis for evaluating field-based biomagnification studies and their reported biomagnification metrics for assessing the biomagnification potential of substances. To test the effectiveness of our proposed guidelines and weight of evidence meta-analysis, we reviewed over 25 field studies investigating the biomagnification of decabromodiphenyl ethane (DBDPE), a substance that is considered super-hydrophobic and difficult to test in bioconcentration tests. Approximately half of the field studies that investigated trophic magnification of DBDPE in food webs or biomagnification of DBDPE in predator-prey interactions were considered of acceptable quality, whereas no studies were of high quality. Quality scores of studies statistically decreased with increasing TMF (r2 = 0.261, p = .035) and/or BMF (r2 = 0.238, p = .0024). The weight of evidence meta-analysis indicated with a high level of confidence that concentrations of DBDPE do not biomagnify in top predators and within food-webs. Given the increasing importance of the TMF and BMF for bioaccumulation assessments and the apparent deficiencies in current biomagnification studies identified in this meta-analysis for DBDPE, there is an urgent need to adopt standardized guidelines and procedures for both conducting and evaluating field-based biomagnification studies.

Keywords: bioaccumulation; biomagnification; decabromodiphenylethane; trophic magnification; weight-of-evidence.

Figure 1.

(A) Frequency of decabromodiphenyl ethane (DBDPE) reported as not detected in biota (ND; n = 5) or reported with a trophic magnification factor (TMF) < 1 (n = 9), a TMF = 1 (n = 3), or a TMF > 1 (n = 2) within trophic magnification field studies of food webs. (B) Frequency of DBDPE reported as ND (n = 21) or reported with a biomagnification factor (BMF) < 1 (n = 22) or a BMF > 1 (n = 11) in biomagnification field studies focused on specific predator-prey interactions.

Figure 2.

(A) Relationship between trophic magnification factors (TMFs) and overall quality scores of field studies. (B) Relationship between biomagnification factors (BMFs) and overall quality scores of field studies. Blue lines represent the linear regression between the associated quality scores and logarithmic TMFs (score = 51.9–6.68 × log₁₀TMF) and/or BMFs (score = 42.1–8.94 × log₁₀BMF). Shaded grey areas represent the 95% confidence interval of the slopes. Solid red lines represent a TMF = 1 or a BMF = 1 (i.e., no biomagnification on average). Dashed red lines represent the quality classifications of unacceptable (≤ 50%), acceptable (> 50% to < 80%), or high quality (≥ 80%).

Figure 3.

(A) Relative importance or contribution of each criterion to the overall R² that measures the proportion of variation in the logarithmic trophic magnification factors (TMFs). (B) Relative contribution of each criterion to the overall R² that measures the proportion of variation in the logarithmic biomagnification factors (BMFs). Error bars represent 95% bootstrap confidence intervals.