Fish consumption and mercury exposure among Louisiana recreational anglers.

BACKGROUND: Methylmercury (MeHg) exposure assessments among average fish consumers in the United States may underestimate exposures among U.S. subpopulations with high intakes of regionally specific fish. OBJECTIVES: We examined relationships among fish consumption, estimated mercury (Hg) intake, and measured Hg exposure within one such potentially highly exposed group, recreational anglers in the state of Louisiana, USA. METHODS: We surveyed 534 anglers in 2006 using interviews at boat launches and fishing tournaments combined with an Internet-based survey method. Hair samples from 402 of these anglers were collected and analyzed for total Hg. Questionnaires provided information on species-specific fish consumption during the 3 months before the survey. RESULTS: Anglers' median hair Hg concentration was 0.81 µg/g (n = 398; range, 0.02-10.7 µg/g); 40% of participants had levels >1 µg/g, which approximately corresponds to the U.S. Environmental Protection Agency's reference dose. Fish consumption and Hg intake were significantly positively associated with hair Hg. Participants reported consuming nearly 80 different fish types, many of which are specific to the region. Unlike the general U.S. population, which acquires most of its Hg from commercial seafood sources, approximately 64% of participants' fish meals and 74% of their estimated Hg intake came from recreationally caught seafood. CONCLUSIONS: Study participants had relatively elevated hair Hg concentrations and reported consumption of a wide variety of fish, particularly locally caught fish. This group represents a highly exposed subpopulation with an exposure profile that differs from fish consumers in other regions of the United States, suggesting a need for more regionally specific exposure estimates and public health advisories.

Sensitivity analysis of the pressure-based direct integrity test for membranes used in drinking water treatment.

We conducted a sensitivity analysis of the commonly employed pressure-based direct integrity test (DIT), the most sensitive test for defects in low-pressure hollow fiber (LPHF) microfiltration and ultrafiltration systems used in drinking water treatment. Incorporating uncertainty to assess the practice of DIT, we find the resolution in some tests may be insufficient to verify the presence of a barrier to oocysts of Cryptosporidium. Applying distributions and boundaries derived from literature and practice, we solved for the defect size resolution (DSR) using Monte Carlo and Probability Bounds Analysis for five commercial membrane designs. Surface tension was modeled using annual temperature profiles from three rivers. Contact angle measurement error and variability were derived from literature, respectively, as a standard deviation of 5.7 degrees and +/- 9.6 degrees median change due to natural organic matter (NOM) fouling. These measures of contact angle uncertainty and variability were combined in a normal distribution with the discrete values currently applied. Additionally we considered model uncertainty, applying the maximum bubble pressure method, an established method of surface tension measurement in liquids in which the maximum air pressure in a submerged capillary is developed after the contact angle becomes zero prior to bubble formation. Where the DSR exceeds 3 microm the test design is not compliant with applicable drinking water regulations. Implications include uncertain and variable log-removal values (LRV) as determined by DIT due to the possible emergence of defects large enough to allow oocysts to pass without detection by the DIT. Specifically, we found the DSR may exceed 3 microm and may be as large as 8 microm. With the variable contact angle model, all lower bound possibilities are compliant, whereas the upper bound is over 80% noncompliant for three of five commercial designs. Using the Maximum Bubble Pressure Method, the lower bounds in three designs start to exceed 3 microm for between 50 and 100% of the produced water, whereas the upper bounds of the DSR completely exceed 3 microm for four of five commercial designs examined.

Effect of sediment remediation on polychlorinated biphenyl concentrations in tomatoes grown near New Bedford Harbor.

Measurements of polychlorinated biphenyl (PCB) congener concentrations and profiles from produce grown near New Bedford Harbor, Massachusetts, USA, before, during, and after remediation of PCB-contaminated sediment are presented. Samples of tomatoes collected from locations upwind and downwind relative to harbor contamination are compared with the use of measurements of 47 individual PCB congeners. The PCB concentration in the locally grown tomatoes, as expressed by the sum of congeners, is highest during the period of harbor dredging and drops to its lowest point after remediation, which included dredging and excavation. The downwind location is characterized by higher concentrations of PCBs than the upwind location in every time period. Principal component analysis is used to distinguish both the effect of remediation over time and the effect of cultivation location on the congener profiles. Evidence of the PCB congener profile representing the contaminated harbor sediments is strongest during the dredging period and in the downwind location. These results have important implications for understanding human exposure via the food chain and highlight the importance of considering exposure pathways related to atmospheric transport during remediation of contaminated sediments.

Importance of uncertainty and variability to predicted risks from trophic transfer of PCBs in dredged sediments.

Biomagnification of organochlorine and other persistent organic contaminants by higher trophic level organisms represents one of the most significant sources of uncertainty and variability in evaluating potential risks associated with disposal of dredged materials. While it is important to distinguish between population variability (e.g., true population heterogeneity in fish weight, and lipid content) and uncertainty (e.g., measurement error), they can be operationally difficult to define separately in probabilistic estimates of human health and ecological risk. We propose a disaggregation of uncertain and variable parameters based on: (1) availability of supporting data; (2) the specific management and regulatory context (in this case, of the U.S. Army Corps of Engineers/U.S. Environmental Protection Agency tiered approach to dredged material management); and (3) professional judgment and experience in conducting probabilistic risk assessments. We describe and quantitatively evaluate several sources of uncertainty and variability in estimating risk to human health from trophic transfer of polychlorinated biphenyls (PCBs) using a case study of sediments obtained from the New York-New Jersey Harbor and being evaluated for disposal at an open water off-shore disposal site within the northeast region. The estimates of PCB concentrations in fish and dietary doses of PCBs to humans ingesting fish are expressed as distributions of values, of which the arithmetic mean or mode represents a particular fractile. The distribution of risk values is obtained using a food chain biomagnification model developed by Gobas by specifying distributions for input parameters disaggregated to represent either uncertainty or variability. Only those sources of uncertainty that could be quantified were included in the analysis. Results for several different two-dimensional Latin Hypercube analyses are provided to evaluate the influence of the uncertain versus variable disaggregation of model parameters. The analysis suggests that variability in human exposure parameters is greater than the uncertainty bounds on any particular fractile, given the described assumptions.

Using GIS and historical records to reconstruct residential exposure to large-scale pesticide application.

Investigation of pesticide impacts on human health depends on good measures of exposure. Historical exposure data are needed to study health outcomes, such as cancer, that involve long latency periods, and other outcomes that are a function of the timing of exposure. Environmental or biological samples collected at the time of epidemiologic study may not represent historical exposure levels. To study the relationship between residential exposure to pesticides and breast cancer on Cape Cod, Massachusetts, historical records of pesticide use were integrated into a geographic information system (GIS) to estimate exposures from large-scale pesticide applications between 1948 and 1995. Information on pesticide use for gypsy moth and other tree/vegetative pest control, cranberry bog cultivation, other agriculture, mosquito control, recreational turf management, and rights-of-way maintenance is included in the database. Residents living within or near pesticide use areas may be exposed through inhalation due to drift and volatilization and through dermal contact and ingestion at the time of application or in later years from pesticides that deposit on soil, accumulate in crops, or migrate to groundwater. Procedures were developed to use the GIS to estimate the relative intensity of past exposures at each study subject's Cape Cod addresses over the past 40 years, taking into account local meteorological data, distance and direction from a residence to a pesticide use source area, size of the source area, application by ground-based or aerial methods, and persistent or nonpersistent character of the pesticide applied. The resulting individual-level estimates of relative exposure intensity can be used in conjunction with interview data to obtain more complete exposure assessment in an epidemiologic study. While the database can improve environmental epidemiological studies involving pesticides, it simultaneously illustrates important data gaps that cannot be filled. Studies such as this one have the potential to identify preventable causes of disease and guide public policies.