The paper builds on existing literature, highlighting current understanding and identifying unresolved issues about MeHg exposure, health effects, and risk assessment, and concludes with a consensus statement. Methylmercury is a potent toxin, bioaccumulated and concentrated through the aquatic food chain, placing at risk people, throughout the globe and across the socioeconomic spectrum, who consume predatory fish or for whom fish is a dietary mainstay. Methylmercury developmental neurotoxicity has constituted the basis for risk assessments and public health policies. Despite gaps in our knowledge on new bioindicators of exposure, factors that influence MeHg uptake and toxicity, toxicokinetics, neurologic and cardiovascular effects in adult populations, and the nutritional benefits and risks from the large number of marine and freshwater fish and fish-eating species, the panel concluded that to preserve human health, all efforts need to be made to reduce and eliminate sources of exposure.

Methylmercury exposure and health effects in humans: a worldwide concern.

A global perspective on cadmium pollution and toxicity in non-occupationally exposed population

Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of individuals that can result in compositional and functional changes of ecosystems. Using multiple and independent monitoring networks, we report population losses across much of the North American avifauna over 48 years, including once-common species and from most biomes. Integration of range-wide population trajectories and size estimates indicates a net loss approaching 3 billion birds, or 29% of 1970 abundance. A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period. This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function, and services.

https://science.sciencemag.org/content/sci/early/2019/09/18/science.aaw1313.full.pdf

Decline of the North American avifauna

We review the ecological rationale behind the potential compatibility between top predators and biodiversity conservation, and examine their effectiveness as surrogate species. Evidence suggests that top predators promote species richness or are spatio-temporally associated with it for six causative or noncausative reasons: resource facilitation, trophic cascades, dependence on ecosystem productivity, sensitivity to dysfunctions, selection of heterogeneous sites and links to multiple ecosystem components. Therefore, predator-centered conservation may deliver certain biodiversity goals. To this aim, predators have been employed in conservation as keystone, umbrella, sentinel, flagship, and indicator species. However, quantitative tests of their surrogate-efficacy have been astonishingly few. Evidence suggests they may function as structuring agents and biodiversity indicators in some ecosystems but not others, and that they perform poorly as umbrella species; more consensus exists for their efficacy as sentinel and flagship species. Conservation biologists need to use apex predators more cautiously, as part of wider, context-dependent mixed strategies.

/pdf/top-predators-as-conservation-tools-ecological-rationale-1lfmzkddjm.pdf

Top Predators as Conservation Tools: Ecological Rationale, Assumptions, and Efficacy

This public health statement tells you about chromium and the effects of exposure to it.The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term federal clean-up activities. Chromium has been found in at least 1,127 of the 1,699 current or former NPL sites. Although the total number of NPL sites evaluated for this substance is not known, the possibility exists that the number of sites at which chromium is found may increase in the future as more sites are evaluated. This information is important because these sites may be sources of exposure and exposure to this substance may be harmful.When a substance is released either from a large area, such as an industrial plant, or from a container, such as a drum or bottle, it enters the environment. Such a release does not always lead to exposure. You can be exposed to a substance only when you come in contact with it. You may be exposed by breathing, eating, or drinking the substance, or by skin contact.If you are exposed to chromium, many factors will determine whether you will be harmed. These factors include the dose (how much), the duration (how long), the form (chromium VI as opposed to chromium III), and how you come in contact with it. You must also consider any other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, and state of health.

Toxicological Profile for Chromium

Marine birds are useful as bioindicators of environmental pollution in estuarine and marine environments because they are often at the top of the food chain, ubiquitous, and many are abundant and common, making collecting possible. Seabirds have the advantage of being large, wide-ranging, conspicuous, abundant, long-lived, easily observed, and important to people. Many species are at the top of the food chain where they bioaccumulate contaminants with age. One disadvantage is that many species are migratory, making it difficult to determine where exposure occurred. This can be eliminated by using sedentary species or young birds that obtain all their food from parents. Further, noninvasive collection of feathers can be used to assess heavy metal levels, both from current collections and from historical collections in museums dating back centuries. Marine birds can be used as bioindicators in many ways, including tissue levels of contaminants, epidemiological field studies of effects, and experimental and laboratory studies of dose and effects. Examples from our research indicate some of the ways marine birds can be useful as indicators and sentinels of contamination, particularly by using young birds and feathers.

http://www.avesmarinhas.com.br/1%20-%20Marine%20Birds%20as%20Sentinels%20of%20Environmental%20Pollution.pdf

Marine Birds as Sentinels of Environmental Pollution

Most attention to the risks from fish consumption has focused on recreational anglers and on fish caught by individuals, but the majority of fish that people eat are purchased from commercial sources. We examined mercury levels in three types of fish (tuna, flounder, bluefish) commonly available in New Jersey stores, sampling different regions of the state, in communities with high and low per capita incomes, and in both supermarkets and specialty fish markets. We were interested in species-specific levels of mercury in New Jersey fish and whether these levels were similar to data generated nationally by the Food and Drug Administration (FDA; mainly from 1990 to 1992) on the same types of fish. Such information is critical for providing public health advice. We were also interested in whether mercury levels in three common species of fish differed by region of the state, economic neighborhood, or type of store. We found significant species differences, with tuna having the highest levels and flounder the lowest levels. There were no significant differences in mercury levels as a function of type of store or economic neighborhood. There was only one regional difference: flounder from fish markets along the Jersey shore had higher mercury levels than flounder bought in other markets. We also examined mercury levels in six other commonly available fish and two shellfish from central New Jersey markets. There were significant differences in availability and in mercury levels among fish and shellfish. Both shrimp and scallops had total mercury levels 50% of markets) would select flounder, snapper, bluefish, and tuna (tuna had the highest mercury value), and those selecting only for price would select whiting, porgy, croaker, and bluefish (all with average mercury levels < 0.3 ppm wet weight). Flounder was the fish with the best relationship among availability, cost, and low mercury levels. We suggest that state agencies responsible for protecting the health of their citizens should obtain information on fish availability in markets and fish preferences of diverse groups of citizens and use this information to select fish for analysis of contaminant levels, providing data on the most commonly eaten fish that will help people make informed decisions about risks from fish consumption.

Mercury in commercial fish: optimizing individual choices to reduce risk.

Framework for gender differences in human and animal toxicology.

Vigilance in vertebrates is often inversely related to group size. We present evidence that distance to bushes and location within the herd are also critical factors in vigilance in springbok (Antidorcas marsupialis) in Etosha National Park, Namibia, where they are the preferred prey of cheetahs (Acinonyx jubatus). Most springbok feed in heterospecific herds, both by grazing on grass and browsing on bushes. We studied 1245 animals; variations in vigilance (time alert) were explained by location within the herd, distance to bushes and roads, number of springbok in each herd, and gender and age. Vigilance time decreased with increasing herd size, with increasing distance to bushes and roads, and with density. Springbok on the edge of herds devoted significantly more time to vigilance than did those in other locations, and vigilance in edge animals decreased with group size. Adults were more vigilant than young, and males were more vigilant than females. Position within the herd, and distance from bushes, were the most important variables influencing vigilance. Location in the herd and gender/age affected both browsing and grazing springbok, although other factors accounted for the differences in vigilance between browsing and grazing springbok: 1) group size was not significant for browsers, but it was for grazers, and 2) distances to bushes and road were not significant for browsers, but they were for grazers. These data relate to the risk from predators and the benefits from other group members. Springbok in bushes cannot see all members of the herd, cannot derive early warning from many group members, and are more at risk from predators because the latter can hide in the bushes.

Factors affecting vigilance in springbok: importance of vegetative cover, location in herd, and herd size

Several species of herons and egrets frequently nest in colonies in areas where humans also concentrate. Since the birds feed on intermediate-sized fish that themselves concentrate pollutants, they can be used not only to assess the levels of contaminants in avian tissues but as indicators of contaminants in the environment. The concentration of heavy metals and selenium in the breast feathers of fledgling black-crowned night herons Nycticorax nycticorax and Chinese pond herons Ardeola bacchus from the Tu Jing Yan heronry outside Chengdu, Szechuan Province in China; and from fledgling black-crowned night heron, little egret Egretta garzetta, great egret Egretta alba and cattle egret Bubulcus ibis from the Mai Po heronry in Hong Kong, were determined. Breast feathers were also collected from adult great egrets in Hong Kong. Adult great egrets had significantly higher levels of all heavy metals than did young great egrets. There were no significant interspecific differences in metal levels among the young at Szechuan China, except for chromium (pond herons had higher levels). There were significant differences among the young nesting at Hong Kong for all metals examined. Great egrets had lower, and night herons had higher, levels of lead than the other young. Night herons also had the highest levels of cadmium, manganese, and selenium compared to the other young. Great egret chicks had the lowest mercury levels, while little egret had the highest levels. Lead levels for all the birds in both Hong Kong and Szechuan were among the highest in the world, and this was attributed to the continued use of leaded gasoline.

Michael Gochfeld

Papers

Marine Birds as Sentinels of Environmental Pollution

Mercury in commercial fish: optimizing individual choices to reduce risk.

Framework for gender differences in human and animal toxicology.

Factors affecting vigilance in springbok: importance of vegetative cover, location in herd, and herd size

Heavy metal and selenium levels in feathers of young egrets and herons from Hong Kong and Szechuan, China