arsenic poisoning

Arsenic and many of its compounds are especially potent poisons. Arsenic disrupts ATP production through several mechanisms.

Citric acid cycle

At the level of the citric acid cycle, arsenic inhibits pyruvate dehydrogenase and by competing with phosphate it uncouples oxidative phosphorylation, thus inhibiting energy-linked reduction of NAD+, mitochondrial respiration, and ATP synthesis.

Hydrogen peroxide production is also increased, which might form reactive oxygen species and oxidative stress.

These metabolic interferences lead to death from multi-system organ failure, probably from necrotic cell death, not apoptosis.

A post mortem reveals brick red colored mucosa, due to severe hemorrhage. Although arsenic causes toxicity, it can also play a protective role.

Toxic

Elemental arsenic and arsenic compounds are classified as "toxic" and "dangerous for the environment" in the European Union under directive 67/548/EEC.

The International Agency for Research on Cancer (IARC) recognizes arsenic and arsenic compounds as group 1 carcinogens, and the EU lists arsenic trioxide, arsenic pentoxide and arsenate salts as category 1 carcinogens.

Arsenic is known to cause arsenicosis due to its manifestation in drinking water, “the most common species being arsenate [HAsO42- ; As(V)] and arsenite [H3AsO3 ; As(III)]”. The ability of arsenic to undergo redox conversion between As(III) and As(V) makes its availability in the environment more abundant.

According to Croal, Gralnick, Malasarn, and Newman, “[the] understanding [of] what stimulates As(III) oxidation and/or limits As(V) reduction is relevant for bioremediation of contaminated sites (Croal). The study of chemolithoautotrophic As(III) oxidizers and the heterotrophic As(V) reducers can help the understanding of the oxidation and/or reduction of arsenic.[34]

Treatment of chronic arsenic poisoning is easily accomplished. British anti-Lewisite (dimercaprol) is prescribed in dosages of 5 mg/kg up to 300 mg each 4 hours for the first day. Then administer the same dosage each 6 hours for the second day. Then prescribe this dosage each 8 hours for eight additional days.

Arsenic in drinking water

Arsenic contamination of groundwater has led to a massive epidemic of arsenic poisoning in Bangladesh[36] and neighbouring countries. Presently 42 major incidents around the world have been reported on groundwater arsenic contamination.

It is estimated that approximately 57 million people are drinking groundwater with arsenic concentrations elevated above the World Health Organization’s standard of 10 parts per billion. However, a study of cancer rates in Taiwan suggested that significant increases in cancer mortality appear only at levels above 150 parts per billion.

The arsenic in the groundwater is of natural origin, and is released from the sediment into the groundwater due to the anoxic conditions of the subsurface. This groundwater began to be used after local and western NGOs and the Bangladeshi government undertook a massive shallow tube well drinking-water program in the late twentieth century. This program was designed to prevent drinking of bacterially contaminated surface waters, but failed to test for arsenic in the groundwater.

Many other countries and districts in South East Asia, such as Vietnam, Cambodia, and Tibet, China, are thought to have geological environments similarly conducive to generation of high-arsenic groundwaters. Arsenicosis was reported in Nakhon Si Thammarat, Thailand in 1987, and the dissolved arsenic in the Chao Phraya River is suspected of containing high levels of naturally occurring arsenic, but has not been a public health problem due to the use of bottled water.