2. What are the ways of arsenic exposure?

Humans are exposed mainly through food, water and cigarette smoking. Food is usually the largest source. Arsenic is one of many hundreds of chemicals present in cigarette smoke. The quantities of arsenic breathed in by non-smokers are very, except in industrially polluted areas. Smokers inhale more because arsenic is one of many hundreds of chemicals present in cigarette smoke.

Many arsenic compounds are quickly transformed and eliminated from the body via the urine. 

3. What are the effects of arsenic exposure?

Many parts of the body may be affected by arsenic, including the skin, gut, lungs, heart, blood vessels, immune system, urinary system, reproductive organs and the nervous system.

Long-term exposure to high levels of arsenic in drinking water can cause thickening and pigment spots in the skin, and cancer of the skin, lungs, bladder or kidney.

Fluorides

4.What are fluorides? Fluorides are organic and inorganic compounds containing the fluorine element.

Generally colourless, the different fluoride compounds are more or less soluble in water and can take the form of a solid, liquid, or gas. Fluorides are important industrial chemicals with a number of uses but the largest uses are for aluminums production, drinking water fluoridation, and the manufacture of fluoridated dental preparations. 

5. How are humans exposed to fluorides?

Food and drinking water typically contain at least small amounts of fluorides.

In drinking water, fluoride can either be naturally present or artificially added for the prevention of dental caries. 

All foodstuffs contain at least small amounts of fluoride. Humans retain 60 to 90% of the fluoride taken in and accumulate almost all of it in their bones and teeth. 

6. What effects have actually been seen in humans?

Fluoride can help prevent cavities, but as the amount taken in increases it can also harm teeth (dental fluorosis) and bones (skeletal fluorosis).

Mercury

7.What is mercury?

Mercury is a chemical element with symbol Hg. It is a liver-coloured metal, and unlike any other metal, it is a liquid at room temperature. It flows so easily and rapidly that it is sometimes called quicksilver.

Mercury compounds have uses in agriculture and industry. Mercury, however, is extremely poisonous and can cause illness or death. After many people realized its dangers, industries and government agencies began trying to reduce the amount of mercury reaching the environment.

8.What are the main uses of mercury?

Mercury has many properties (qualities) that make it useful. For example, mercury expands and contracts evenly when heated or cooled. It also remains liquid over a wide range of temperatures. These properties have prompted its use in thermometers.

9.What compounds does mercury form? Can they be useful for people?

Chemists divide mercury compounds into two groups: (1) mercurous and (2) mercuric. Mercurous compounds include mercurous chloride (Hg₂Cl₂), also called calomel, and mercurous sulphate (Hg₂SO₂). Calomel is an antiseptic used to kill bacteria. Scientists use mercurous sulphate to speed up certain tests on organic compounds.

Mercuric compounds include mercuric chloride (HgCl₂), a powerful poison that surgeons once used to disinfect wounds. Several organic mercuric compounds have important medical uses. For example, diuretics, which doctors use to treat kidney disease, contain these compounds. The antiseptic Mercurochrome is also a mercuric compound.