Mercury is a naturally occurring, silvery-white heavy metal that is liquid at room temperature. It conducts electricity, expands evenly with heat, and bonds easily with other elements. Because of these properties, mercury was once widely used in thermometers, fluorescent lights, dental fillings, and industrial processes.

Today, we know mercury is highly toxic. Even small amounts can harm humans and the environment. The World Health Organization lists mercury among the top ten chemicals of major public health concern.

Photo: Getty Images

How mercury enters the environment

Mercury is released naturally through volcanic eruptions, geothermal activity, and rock weathering. But human activities have greatly increased its circulation.

According to the United Nations Environment Programme, human activities released around 2,220 metric tonnes of mercury into the atmosphere in 2015. Major sources include artisanal and small-scale gold mining, coal-fired power plants, metal smelting, cement production, and waste from mercury-containing products.

In small-scale gold mining, mercury is mixed with crushed ore to extract gold. Heating the mixture releases invisible vapor, which can be inhaled by miners and nearby residents. Mercury then enters the bloodstream and accumulates in the brain, damaging the nervous system.

Even as mercury use declines, old industrial sites, discarded products, and contaminated soils continue to release mercury. Once airborne, mercury can travel thousands of kilometers, cycling through the air, land, and oceans.

Why mercury is dangerous

Mercury is persistent. It does not degrade but changes form and moves through the environment. In water, bacteria can convert inorganic mercury into methylmercury, a highly toxic compound that accumulates in fish and shellfish.

This process, called bioaccumulation, increases mercury levels up the food chain. Large predatory fish, such as tuna and swordfish, often contain the highest concentrations.

When humans eat these fish, methylmercury enters the bloodstream. In pregnant women, it crosses the placenta and reaches the fetal brain.

Even low-level exposure can affect a child’s learning, memory, and motor skills. Some fishing communities see 1.5 to 17 per 1,000 children affected by methylmercury.

Mercury vapor is also harmful when inhaled. Short-term exposure can cause coughing, nausea, chest pain, and lung inflammation. Long-term exposure may lead to tremors, fatigue, memory loss, and kidney damage.

The Minamata Convention

To tackle mercury pollution, countries adopted the Minamata Convention on Mercury in 2013. It is named after Minamata, Japan, where industrial mercury discharges in the 1950s caused one of the worst poisoning disasters in history.

As of 2025, more than 150 countries have joined the Convention. The treaty takes a lifecycle approach to mercury management, covering mining, trade, use, release, and disposal. Key measures include:

• Banning new mercury mines and limiting existing ones;
• Phasing out mercury-added products like thermometers, lamps, and certain cosmetics;
• Restricting mercury use in industries such as chlor-alkali and acetaldehyde production;
• Controlling emissions from coal combustion, metal production, and waste incineration;
• Mandating safe storage, treatment, and disposal of mercury waste, and cleanup of contaminated sites;
• Supporting small-scale gold mining reforms and encouraging mercury-free extraction methods

Photo: UNDP Peru

What UNDP does

UNDP, with support from the Global Environment Facility (GEF), helps developing countries and economies in transition to reduce mercury use and emissions. Our work covers artisanal and small-scale gold mining, healthcare, non-ferrous metals, and consumer products.

UNDP combines advocacy, capacity building, technical assistance, and monitoring to help countries comply with the Minamata Convention. Across 44 countries, our mercury projects aim to eliminate over 210 metric tonnes of mercury.

In artisanal and small-scale gold mining, UNDP, under the GEF-funded planetGOLD programme, has supported the reduction of 20 metric tonnes of mercury in Colombia, 15 metric tonnes of mercury in Indonesia, and 15 metric tonnes of mercury in Peru.

UNDP is also part of the GEF-funded Global Elimination of Mercury in Non-ferrous Metals Initiative (GEMINI). In India and Mexico, UNDP targets to eliminate 24 metric tonnes of mercury pollution.

In healthcare, UNDP helps phase out mercury-containing devices, such as thermometers and sphygmomanometers, while improving waste management. Our ongoing projects are expected to remove 75 tonnes of mercury in China and 99.8 tonnes of mercury and related waste in Sri Lanka.

(Get a full overview of UNDP’s mercury projects here)

Photo: UNDP Peru

COP-6 and beyond

This week Parties to the Minamata Convention are meeting in Geneva. The Sixth Meeting of the Conference of the Parties (COP‑6) will review progress on mercury control and set priorities for the next phase of action.

Delegates will focus on issues such as controlling mercury trade and supply, improving waste management, and reducing releases from artisanal and small‑scale gold mining.

They will also strengthen cooperation with other global environmental agreements and support the full participation of indigenous peoples and local communities.

The Convention’s message remains simple: mercury pollution anywhere is a threat everywhere. Acting together is the only way to protect people and planet.