Due to its exceptional propensity to adhere to valuable metals, mercury has been used for thousands of years to extract gold and silver. According to пᴜmeгoᴜѕ studies, this type of small-scale or “artisanal” mercury extraction has evolved into the main source of mercury contamination in recent years.

In addition to seeping into the soil and rivers from water used in the process and from rain runoff contaminated by materials left over from mining operations, mining releases mercury into the air when it is burned to separate gold from a piece of rock or mud.

Many of these miners operate illegally in developing countries like Peru, where there is little or no regulation, making the practice difficult to undo, said Dave Krabbenhoft, a researcher at the U.S. Geological Survey in Middleton, Wisconsin.

Heavy metal also remains for centuries and is re-emitted from soil and water to the atmosphere, and vice versa. As a volatile element, mercury can evaporate at relatively low temperatures and then be deposited out of the atmosphere through chemical reactions and returned to soil or water bodies. In fact, most of the mercury that reaches the ocean (after falling from the air or being washed away by rivers) is “legacy” mercury that was already present in the environment, much of it dumped by smokestacks or mined from gold mines. hundreds of years ago. Years ago, Krabbenhoft tells LiveScience.

Scientists pay special attention to oceanic mercury because that is where the element is converted to methylmercury, the toxic carbon-containing form that accumulates in fish; Eating shellfish is the main way humans are exposed to the heavy metal, he said. Most methylmercury is produced by microbes in dark conditions, according to a study published earlier this year in the journal Nature Geoscience.

However, there is some promising news: Delegates from countries around the world will meet in Minamata, Japan, in early October to formalize an agreement to reduce mercury pollution in several ways. That news, however, is tempered by a review published Thursday in the journal Science that suggests mercury levels in the environment will likely continue to rise for decades, said Krabbenhoft, a co-author of the study.

Reduce mercury

The goals of the meeting include closing all mercury mines in signatory countries within 15 years of the agreement coming into force. Many consumer products containing mercury are also expected to be phased out, and dental amalgams containing mercury will be “phased out,” according to a Science article accompanying the review. Many of the countries where artisanal mining is a problem, especially those in South America, Southeast Asia and Africa, will also make efforts to try to combat this problem, Science reported.

The convention will be held in Minamata, in part, because the city is home to the first and most notorious case of mercury poisoning: 65 years ago, a chemical plant released large amounts of methylmercury in its waste into the ocean, where it accumulated in fish and poisoned Thousands. Many died and many more suffered brain damage, metabolic delay, birth defects and other health problems, said Dr. Philippe Grandjean, a Harvard University epidemiologist who conducted field work in Minamata and was involved in drafting the rules of Convention. But it took years to definitively link the source of the so-called “Minamata disease” to mercury, due in part to resistance from the chemical company that released the mercury, and it took even longer to spur international action, Grandjean said. [The 10 most polluted places in the world]

But Grandjean and others think the convention (whose language has already been worked out and written) doesn’t go far enough. Many of the agreements are voluntary and are qualified with the phrase “when feasible,” notes the Science article.

Grandjean said one of the main problems is that the convention does not do enough to reduce mercury exposure in the short term. In fact, due to the long-lasting nature of the contaminant, “mercury in the environment is going to increase, probably for decades,” as the mercury that is already there remains and the new mercury, although in smaller quantities than before, – finds its way into the environment, Grandjean told LiveScience.

Worse in the short term

One measure people can take to reduce their mercury exposure, Grandjean said, is to eat fish that accumulate less mercury, such as small, short-lived fish like sardines; Methylmercury gradually moves up the food chain and is most common in large, old carnivorous fish, he added. [Is it safe to eat sushi?]

“We have already introduced so much mercury into ecosystems that it will be decades before we can benefit from the UN treaty,” Grandjean said. “In the meantime, we must select our seafood wisely.”

Grandjean hopes efforts to reduce small-scale mining will be successful. But the construction of new coal plants, particularly in China, is not encouraging, as fossil fuels are the second largest source of mercury pollution, Krabbenhoft said. Climate change may also worsen mercury pollution, as a warmer world is expected to lead to more intense flooding and wildfires, both of which release mercury trapped in soil and vegetation, he said.

The convention is a good first step, but the persistent nature of mercury means the situation will get worse before it gets better, Grandjean said, although he is still hopeful that mercury pollution can be curbed.

“Just because we didn’t get an optimal treaty doesn’t mean we lost,” Grandjean said. “We should still consider it a victory, but there is still a lot of work to do.”