Elemental arsenic is a heavy metal which occurs to a limited extent in nature as a steel-grey metal insoluble in water (solubility is less than 1mg/l). It also occurs in black and yellow amorphous (non-crystal) forms. Inorganic arsenic (usually in the As2O3 form) is naturally present in many kinds of rock, particularly in copper and lead ores. When heated, these ores release the arsenic which enters the air as a fine dust which can then be collected and purified. Arsenic is highly reactive and can easily undergo many chemical transformations. Most arsenic compounds can dissolve in water. Arsenic is easily adsorbed by iron and manganese and reacts with clay particles which explains why it is often found in sediments. Some fish and shellfish can accumulate arsenic in their tissues but mostly in a form non-toxic to humans. It has been reported that the total amount taken in from normal sources (food, water, air) for a person is about 50 mg/day.
Canadian Water Quality Guidelines
BENCHMARKS
Interim drinking water guideline
(total) 0.025 mg/l
Protection of freshwater aquatic life
(total) 0.05 mg/l (under review)
Irrigation water
(total) 0.1 mg/l (under review)
Livestock watering
(total) 0.5 - 5.0 mg/l (under review) Ontario Water Quality Objectives (MOEE 1994)
Interim PWQO - protection of aquatic life 0.1 mg/l
Interim PWQO (revised)
under development0.005 mg/l
U.S. EPA
Protection of freshwater aquatic life
total recov. trivalent inorg. arsenic <0.440 mg/l
Protection of saltwater aquatic life
total recov. trivalent inorg. arsenic <0.508 mg/l (acute)
Human health
0.00002 mg/l = 1 in 100,000 risk
Maximum arsenic level
0.05 mg/l
(does not address carcinogenicity and is under review)
Drinking Water Standards
South African Bureau of Standards
0.05 mg/l
World Health Organization
0.05 mg/l
Federal Republic of Germany (1975)
0.04 mg/l
Workplace Air Standards
Occupational Safety and Health Administration (OSHA) exposure limit
0.01 mg/m3 (airborne inorg. As)
over an 8-hour shift
LC50 Values (species mean acute value) (U.S. EPA)
Daphnia magna
4.4 mg/l
Rainbow trout
13 mg/l
Fathead minnow
15 mg/l
HUMAN HEALTH
Inorganic Arsenic
Inorganic arsenic has been recognized as a human poison since ancient times Large oral doses (above 60,000 ppb in food or water) can produce death Arsenic is a known human carcinogen; there may be no safe level of exposure, reduce contact to the lowest possible level. Arsenic and arsenic-compounds may cause malformation of the fetus; potentially teratogenic. Arsenic is widely distributed in the body and the trivalent form is excreted very slowly and accumulates in tissue. The liver transforms a portion of the ingested inorganic arsenic to a less harmful organic form. Both inorganic and organic forms of arsenic are excreted through urine. Most of the arsenic will leave the body after a few days but some will remain for several months and even longer. Symptoms following ingestion of arsenic (dose ranging from about 300 to 30,000 ppb in food and water): irritation of the stomach and intestines, with symptoms such as pain, nausea, vomiting, and diarrhea. Other possible effects: decreased production of red and white blood cells, abnormal heart rhythm, blood vessel damage, and impaired nerve function causing a "pins and needles" sensation in your hands and feet. Most characteristic effect of long-term oral exposure to inorganic arsenic is a pattern of skin changes: darkening of the skin and the appearance of small corns or warts on the palms, soles, and torso, a small number of the corns may ultimately develop into skin cancer. Also, weight loss, nausea and diarrhea alternating with constipation, hair loss. Horizontal white lines on the fingernails and toenails are commonly seen in chronic arsenic poisoning. Examples of chronic poisoning have been reported for water with arsenic concentrations of 210 mg/l to 1000 mg/l (Aston et al., 1975). Swallowing arsenic has also been reported to increase the risk of cancer in the liver, bladder, kidney, and lung. Symptoms following breathing high levels of inorganic arsenic (probably above 100 micrograms per cubic meter): sore throat and irritated lungs. Coughing, chest pain, giddiness, headache. Possible skin effects as mentioned above. These effects are usually not serious. Inhaled inorganic arsenic increases the risk of lung cancer. Chronic inhalation of arsenic compounds: weakness, loss of appetite, nausea, vomiting, diarrhea, perforation of the nasal septum, skin lesions, nerve inflammation in the hands and feet. Direct skin contact with inorganic arsenic compounds: corrosive. Moist membranes such as around the eyes and nose are most sensitive. Skin may become irritated with some redness and swelling. Skin contact is not likely to lead to any serious internal effects. There is some evidence that the small amounts of arsenic in the normal diet (10-50 ppb) may be beneficial to one's health. No cases of arsenic deficiency in humans have ever been reported. Organic arsenic Almost no information is available on the effects of organic arsenic compounds in humans. Thus, if you are exposed to high doses of an organic arsenic compound, you might develop nerve injury, stomach irritation, or other effects, but this is not known for certain.
Blood, urine, hair or fingernails tests can be performed to determine whether a person has been exposed to above-normal arsenic levels. Urine test is most useful to detect recent exposure whereas hair and fingernail tests are most useful for high level exposure over the last 6 to 12 months.
In urine test, concentration should not be greater than 100 micrograms/gram creatinine.
Arsenic is acutely toxic to animals and may cause death. In animals, chronically exposed, the effets may include shortened life expectancy, decrease in reproduction, and behavioural effects. Arsenic appears to be more toxic to aquatic species than land animals.
Studies in animals show that doses of arsenic that are large enough to cause illness in pregnant females may cause low birth weight, fetal malformations, or even fetal death. Animals fed a diet with unusually low concentrations of arsenic did not gain weight normally. They also became pregnant less frequently than animals fed a diet containing a normal amount of arsenic. Further, the offspring from these animals tended to be smaller than normal, and some died at an early age. Organic arsenic Studies in animals show that most organic arsenic compounds are less toxic than the inorganic forms.However, high doses can produce some of the same effects.
Dr. Ronald Brecher, "Chemical Corner"
MEDICAL TESTS
ANIMAL HEALTH
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