Health risks from hydroelectric projects, pesticides’ exposure

• 2016 may be hottest on record: El Niño, emissions are blamed for sweltering temperatures
As Nigeria intensifies efforts towards boosting electricity supply by establishing more hydroelectric projects and improving agricultural outcomes with pesticides, scientists have warned that these practices are associated with health risks.

According to a new study published in Environmental Science & Technology, over 90 percent of potential new Canadian hydroelectric projects are likely to increase concentrations of the neurotoxin methylmercury in food webs near indigenous communities.

The research from Harvard University, United States (U.S.), found potential human health impacts of hydroelectric projects and identified areas where mitigation efforts, such as removing the top layer of soil before flooding, would be most helpful. The works uses factors such as soil carbon and reservoir design to forecast methylmercury increases for 22 hydroelectric reservoirs under consideration or construction in Canada.

According to the World Health Organisation (WHO), elemental and methylmercury are toxic to the central and peripheral nervous systems. The inhalation of mercury vapour can produce harmful effects on the nervous, digestive and immune systems, lungs and kidneys, and may be fatal. The inorganic salts of mercury are corrosive to the skin, eyes and gastrointestinal tract, and may induce kidney toxicity if ingested.

Neurological and behavioural disorders may be observed after inhalation, ingestion or dermal exposure of different mercury compounds. Symptoms include tremors, insomnia, memory loss, neuromuscular effects, headaches and cognitive and motor dysfunction. Mild, subclinical signs of central nervous system toxicity can be seen in workers exposed to an elemental mercury level in the air of 20 μg/m3 or more for several years. Kidney effects have been reported, ranging from increased protein in the urine to kidney failure.

The Thomas D. Cabot Associate Professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Harvard T.H. Chan School for Public Health and senior author of the study, Elsie Sunderland, said: “The human and ecological impacts associated with increased methylmercury exposures from flooding for hydroelectric projects have only been understood retrospectively, after the damage is done.

“This paper establishes a prospective framework for forecasting the impacts of proposed hydroelectric development on local communities.”

Meanwhile, the World Meteorological Orgnaization (WMO) has revealed that 2016 could be the warmest since records began, thanks to a strong El Niño and fossil fuel emissions.

According to the United Nation’s (UN’s) weather agency, global warming has stoked more floods, fires and rising sea levels.The WMO has said that 2016 will be the warmest since records began in the late 19th century, with average surface temperatures 1.2°C (2.2°F) above pre-industrial times, driven by a strong El Niño and man-made carbon emissions

The WMO said this year would be the warmest since records began in the late 19th century, with average surface temperatures 1.2°C (2.2°F) above pre-industrial times.Sixteen of the 17 hottest years recorded have been in this century.

Data from the UN refugee agency said 19.2 million people were displaced by weather, water, climate and hazards such as earthquakes in 2015, more than twice as many as for conflict and violence, it said.

Also, pesticide exposure in farmworkers from agricultural communities is associated with changes in the oral microbiome. This is the first study to demonstrate such a correlation in humans.

The research is published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.In the study, the investigators sampled oral swabs from 65 farmworkers and 52 non-farmworker adults from the Yakima Valley (Washington) community agricultural cohort during the spring and summer (2005), when farmworkers can undergo high pesticide exposures while working in recently sprayed orchards, thinning the fruit and pruning; and during winter (2006), when exposures are quite low.

Concurrently, they measured blood levels of organophosphate pesticides in the study subjects.The most important finding was that among those farmworkers in whom the organophosphate pesticide, Azinphos-methyl was detected in the blood, the researchers found “significantly reduced abundances of seven common taxa of oral bacteria, including Streptococcus, one of the most common normal microbiota in the mouth,” said first author, Ian B. Stanaway, a PhD candidate in Environmental Toxicology in Elaine M. Faustman’s lab at the University of Washington, Seattle. Changes in populations, species, and strains of Streptococcus, as well as from the genus, Halomonas, remained particularly low during the following winter.

The investigators also saw a pesticide-associated spring/summer general reduction in bacterial diversity in the study subjects, which persisted into the winter, suggesting that “long-lasting effects on the commensal microbiota have occurred,” according to the report.

Predictably, farmworkers had greater blood concentrations of pesticide, and greater changes in their oral microbiota than local, non-farm-working adults.

Microbes convert naturally occurring mercury in soils into potent methylmercury when land is flooded, such as when dams are built for hydroelectric projects. The methylmercury moves into the water and animals, magnifying as it moves up the food chain. This makes the toxin especially dangerous for indigenous communities living near hydroelectric projects because they tend to have diets rich in local fish, birds and marine mammals such as seals.

To understand how methylmercury impacts human populations, the Harvard team studied three Inuit communities downstream from the proposed Muskrat Falls hydroelectric facility in Labrador. The project will require the flooding of land bordering the Churchill River, upstream from an estuarine fjord called Lake Melville.

Sunderland and her team have been working in this region since 2012, conducting a multi-pronged investigation into how methylmercury accumulates in the ecosystem and how it may impact communities who rely on the ecosystem for food and resources.