Delegates from around 140 countries have agreed to adopt a treaty limiting the use of hazardous mercury.

The world's first legally-binding treaty on mercury, reached Saturday after a week of talks in Geneva, Switzerland, aims to reduce global emission levels of the toxic heavy metal, which pose risks to human health and the environment.

In a new report, the U.N. Environment Program found that worldwide, nearly 2,000 tons of mercury are emitted into the air from human activities every year. Much of this toxic substance eventually becomes deposited on vegetation, in the soil, and in oceans, lakes and rivers.

The deputy head of UNEP's Chemical Branch said this week that much human exposure to mercury is through the consumption of contaminated fish.

Mercury affects the brain and nervous system and can cause physical and mental development problems in children. Pregnant women who ingest mercury can pass the toxic effects to their unborn children.

The U.N. Environment Program finds the global demand for mercury is decreasing somewhat, with many developed countries taking measures to reduce mercury use. But it notes mercury use is increasing in developing countries.