انت هنا الان : شبكة جامعة بابل > موقع الكلية > نظام التعليم الالكتروني > مشاهدة المحاضرة

Arsenic poisoning

METAL TOXICITY

الدكتورة سجال فاضل فرهود الجبوري

Arsenic poisoning kills by inhibition of essential metabolic enzymes, leading to death from multi-system organ failure. It primarily inhibits enzymes that require lipoic acid as a cofactor, such as pyruvate and alpha-ketoglutarate dehydrogenase. Because of this, substrates before the dehydrogenase steps accumulate, such as pyruvate (and lactate). It particularly affects the brain, causing neurological disturbances and death.

 Toxicity

The toxicity of arsenic and its compounds is highly variable. Organic forms appear to have a lower toxicity than inorganic forms of arsenic. Research has shown that arsenites (trivalent forms) have a higher acute toxicity than arsenates (pentavalent forms). The acute minimal lethal dose of arsenic in adults is estimated to be 70 to 200 mg or 1 mg/kg/day. Most reported arsenic poisonings are not caused by elemental arsenic, but by one of arsenics compounds, especially arsenic trioxide, which is approximately 500 times more toxic than pure arsenic.^]

Symptoms:

  Include violent stomach pains in the region of the bowels; tenderness and pressure; retching; excessive saliva production; vomiting; sense of dryness and tightness in the throat; thirst; hoarseness and difficulty of speech; the matter vomited, greenish or yellowish, sometimes streaked with blood; diarrhea; tenesmus; sometimes excoriation of the anus; urinary organs occasionally affected with violent burning pains and suppression; convulsions and cramps; clammy sweats; lividity of the extremities; countenance collapsed; eyes red and sparkling; delirium; death.

Symptoms of arsenic poisoning start with mild headaches and can progress to lightheadedness and usually, if untreated, will result in death.

Arsenic poisoning can lead to a variety of problems, from skin cancer to keratoses of the feet.

Chronic exposure to inorganic arsenic may lead to cutaneous hyperpigmentation.

 Diagnosis

There are tests available to diagnose poisoning by meauring arsenic in blood, urine, hair, and fingernails. The urine test is the most reliable test for arsenic exposure within the last few days. Urine testing needs to be done within 24–48 hours for an accurate analysis of an acute exposure. Tests on hair and fingernails can measure exposure to high levels of arsenic over the past 6–12 months. These tests can determine if one has been exposed to above-average levels of arsenic. They cannot predict, however, whether the arsenic levels in the body will affect health.

 Treatment

Chemical and synthetic methods are now used to treat arsenic poisoning. Dimercaprol and Succimer are chelating agents which sequester the arsenic away from blood proteins and are used in treating acute arsenic poisoning. The most important side-effect is hypertension. Dimercaprol is considerably more toxic than succimer.

Occupational & Unintentional poisoning

In addition to its use as a poison, arsenic was used medicinally for centuries and was used extensively to treat syphilis before penicillin was introduced. Arsenic was replaced as a therapeutic agent by sulfa drugs and then by antibiotics. Arsenic was also an ingredient in many tonics.. In addition, during the Victorian era, some women used a mixture of vinegar, chalk, and arsenic applied topically to whiten their skin. The use of arsenic was intended to prevent aging and creasing of the skin, but some arsenic was inevitably absorbed into the blood stream.

Industries that use inorganic arsenic and its compounds include wood preservation, glass production, nonferrous metal alloys, and electronic semiconductor manufacturing. Inorganic arsenic is also found in coke oven emissions associated with the smelter industry.

Occupational exposure to arsenic may occur with copper or lead smelting and wood treatment, among workers involved in the production or application of pesticides containing organic arsenicals. Humans are exposed to arsenic through air, drinking water, and food (meat, fish, and poultry); this food is usually the largest source of arsenic. Arsenic was also found in wine if arsenic pesticides are used in the vineyard. Arsenic is well absorbed by oral and inhalation routes, widely distributed and excreted in urine; most of a single, low-level dose is excreted within a few days after consuming any form of inorganic arsenic. Remains of arsenic in nails and hair can be detected years after the exposure.

chronic arsenic poisoning from drinking water

Chronic arsenic poisoning results from drinking water with high levels of arsenic over a long period of time. This may occur due to arsenic contamination of groundwater. The World Health Organization recommends a limit of 0.01 mg/L (10ppb) of arsenic in drinking water. This recommendation was established based on the limit of detection of available testing equipment at the time of publication of the WHO water quality guidelines. More recent findings show that consumption of water with levels as low as 0.00017 mg/L (0.17ppb) over long periods of time can lead to arsenicosis.