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Hundreds of thousands of documented and undocumented orphaned oil and gas wells exist in the United States (U.S.). These wells have the potential to contaminate water supplies, degrade ecosystems, and emit methane and other air pollutants. Thus, orphaned wells present risks to climate stability and to environmental and human health, which can be reduced by plugging. To quantify environmental risks and opportunities of well plugging at the national level, we analyze data on 81 857 documented orphaned wells across the U.S. We find that > 4.6 million people live within 1 km of a documented orphaned well. 35% of the documented orphaned wells are located within 1 km of a domestic groundwater well, yet only 8% of the wells have groundwater quality data within a 1 km radius. Methane emissions from the documented orphaned wells represent approximately 3%–6% of total U.S. methane emissions from abandoned oil and gas wells, but this estimate is based on measurements at < 0.03% of U.S. abandoned wells. 91% of the documented orphaned wells overlie formations favorable for geologic storage of carbon dioxide and hydrogen, meaning that orphaned well plugging can reduce leakage risks from future storage projects. Finally, we estimate plugging costs for documented orphaned wells to exceed the $4.7 billion federal funding by 30%–80%, emphasizing the importance of prioritizing federal spending on wells with large remediation benefits. Overall, environmental monitoring data are not extensive enough to quantify risks, especially those related to air and water quality and human health. Plugging orphaned wells can provide opportunities for geologic storage of carbon dioxide and hydrogen and geothermal energy development, thereby facilitating efforts to transition to net-zero energy systems. Our analysis on environmental risks and opportunities of orphaned wells provides a framework that can be used to manage the millions of documented and undocumented orphaned wells in the U.S. and abroad.

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.

Polycyclic aromatic hydrocarbons (PAHs) are a large class of organic chemicals typically found as mixtures in the aquatic environment from natural, petrogenic, and pyrogenic sources. People can be exposed to PAHs through ingestion or dermal contact with contaminated sediments or through ingestion of finfish and shellfish exposed to contaminated sediments. Although more than 100 PAHs have been identified, human exposure and risk are commonly evaluated for 18 individual PAHs. Other PAHs, such as alkylated PAHs, likely contribute to biological activity of environmental PAH mixtures; however, insufficient toxicity data are available to quantify their potential risk. This article presents an initial evaluation of the potential for human health risk from exposure to alkylated PAHs in sediment and fish. Individual alkylated PAHs have been observed to have potentially mutagenic, tumor-promoting, or carcinogenic activity. However, except for 1-and 2-methylnaphthalene, insufficient toxicity data are available to quantify toxicity or cancer risk from exposure to individual alkylated PAHs or mixtures of alkylated PAHs. This article describes a proposed strategy to better understand the potential human health risk from exposure to alkylated PAHs. Implementation of this strategy will contribute to evaluations of human exposure to complex PAH mixtures in the environment.

The US Environmental Protection Agency (USEPA) solely assesses the risks brought about by contaminated freshwater and saltwater environments through fish consumption. However, such practice offers unreliable information because it neglects other variables such as the species and parts of the fish that are consumed, the places where the fish are caught, the manner of how it was cooked, and the characteristics of the fish consumers. Vorhees discusses the changes USEPA should implement in its risk assessment practices.

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.

Human health risk assessments of contaminated freshwater and saltwater environments often center on evaluations of risk from consumption of contaminated fish. Based on reports from U.S. states, tribes, territories, and interstate commissions, the U.S. Environmental Protection Agency (USEPA) reported that about 40% of streams, 45% of lakes, and 50% of estuaries that were assessed were not clean enough to support uses such as fishing (USEPA 2000). To quantify risk from fish consumption at any given site, one ideally would have sufficient data about current and potential future fish consumption practices. Such information should include more than just how much fish is consumed, but also the species and fish parts that are consumed, where the fish are caught, how they are prepared and cooked, and characteristics of the fish consumers that are associated with susceptibility to the effects of chemicals in fish. Risk assessors must clearly define the target population of concern, with the goal of quantifying the variability in the rate of fish consumption among members of the target population.

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.