Estimating risk at a Superfund site using passive sampling devices as biological surrogates in human health risk models

Abstract

Passive sampling devices (PSDs) sequester the freely dissolved fraction of lipophilic contaminants, mimicking passive chemical uptake and accumulation by biomembranes and lipid tissues. Public Health Assessments that inform the public about health risks from exposure to contaminants through consumption of resident fish are generally based on tissue data, which can be difficult to obtain and requires destructive sampling. The purpose of this study is to apply PSD data in a Public Health Assessment to demonstrate that PSDs can be used as a biological surrogate to evaluate potential human health risks and elucidate spatio-temporal variations in risk. PSDs were used to measure polycyclic aromatic hydrocarbons (PAHs) in the Willamette River; upriver, downriver and within the Portland Harbor Superfund megasite for 3 years during wet and dry seasons. Based on an existing Public Health Assessment for this area, concentrations of PAHs in PSDs were substituted for fish tissue concentrations. PSD measured PAH concentrations captured the magnitude, range and variability of PAH concentrations reported for fish/shellfish from Portland Harbor. Using PSD results in place of fish data revealed an unacceptable risk level for cancer in all seasons but no unacceptable risk for non-cancer endpoints. Estimated cancer risk varied by several orders of magnitude based on season and location. Sites near coal tar contamination demonstrated the highest risk, particularly during the dry season and remediation activities. Incorporating PSD data into Public Health Assessments provides specific spatial and temporal contaminant exposure information that can assist public health professionals in evaluating human health risks.

Figure 1

Sampling sites on the lower Willamette River 2004–2006. Each site is designated by a yellow circle. Not all sites were used every deployment. The red line indicates the approximate boundaries of the Portland Harbor Superfund megasite.

Figure 2

Σ₁₆PAH and carcinogenic PAHs in PSDs. Mass-to-mass concentration of sum PAHs and sum carcinogenic PAHs in passive sampling devices (PSDs) at sites downriver, upriver and within the Portland Harbor Superfund megasite. Each point represents one observation during the dry season (closed circles), wet season (open circles) or tar removal remediation (triangles). These values were used in place of fish tissue concentrations to calculate exposure for risk assessment models.

Figure 3

Estimated number of cancers, in excess of the background rate, per 1,000,000 individuals exposed to carcinogenic PAHs. Calculations are based on average fish consumption rates; where LFT concentrations have been substituted for fish tissue concentrations. Data from all sites located in each area of the river (upriver, downriver and within the Superfund) were averaged for the wet and dry seasons and observations associated with tar removal remediation activities are presented separately. Error bars represent 95% confidence intervals, based on variability in the PSD measured concentrations for each site-season, and only one observation was made at the downriver site during tar removal. See table 1 for statistical analyses of these data.