Poles A Report About Their Toxic Trail and Safer Alternatives
Appendix A: Chemicals-At-A-Glance
Identity And Uses
Ingredients, including contaminants, inerts, and by-productsArsenicals contain a mixture of ingredients, including arsenic. The most commonly used arsenical is copper chromium arsenate (CCA), which is a mixture of arsenic pentoxide, chromic acid, and copper or cupric oxide, plus secret "inert" ingredients, in prop ortions that vary with the particular product. The chromium in CCA occurs in the more toxic hexavalent, or chromium (VI), form. Although all the active ingredients are toxic to a broad range of organisms, the effects are mostly dominated by the arsenic co mponent.
Trade namesCCA is used under the names Osmose and Wolman among others.
UsageIn 1995: 138,470,000 pounds1; 29,215,000 cubic feet of treated poles; 450,596,000 cubic feet of treated wood.2
AbsorptionArsenic is readily absorbed through ingestion and inhalation. It is absorbed to a lesser extent through the skin.3
Clearing, detoxification, and metabolismIf arsenic is consumed in very small amounts, most will be metabolized by the liver and excreted.4
Acute toxicityIngestion or inhalation of high doses of arsenic can produce pain, nausea, vomiting, and diarrhea. It can also produce characteristic skin lesions, decreased production of red and white blood cells, abnormal heart function, blood vessel damage, liver and/ or kidney injury, impaired nerve function causing a "pins-and-needles" feeling in the feet and hands, and damage to a developing fetus.5
Critical dosesThe lethal oral dose of arsenic for an adult human is 1 to 25 mg arsenic per kg body weight.6
Chronic health effects
Organ damageArsenic poisoning damages mucous membranes, irritates eyes, causes darkening and lesions of the skin, liver inflammation and damage, abnormal heart function, and hearing loss.7
NeurotoxicityArsenic produces disturbances and degeneration of the peripheral nervous system.8
Reproductive toxicity and teratogenicitySpontaneous abortion rates were increased among exposed workers compared to controls. In rodent tests, arsenic increased fetal mortality and birth defects and increased the ratio of males to females in mice.9
ImmunotoxicityEvidence in both animals and humans suggests that arsenic suppresses the immune system.10
Critical dosesWhile some humans can ingest over 150 ug/kg/day without any apparent ill-effects, more sensitive individuals in exposed populations often begin to display one or more of the characteristic signs of arsenic toxicity at oral doses of around 20 ug/kg/day (ab out 1000 to 1500 ug/day for an adult). Doses of 600 to 700 ug/kg/day (around 50,000 ug/day in an adult or 3,000 ug/day in an infant) have caused death in some cases.11
CancerEPA classifies arsenic as a class A, or known human carcinogen. Arsenic ingestion or inhalation has been reported to increase the risk of cancer, especially in the liver, bladder, kidney, and lung.12
MutationsArsenic exposure has been found to increase the frequency of chromosomal abnormalities in highly exposed people.13
Endocrine disruptionThe arsenicals are not known to disrupt the endocrine system.
Bioaccumulation/bioconcentration potentialAlthough small amounts of toxic metals are excreted by organisms, doses of arsenic and associated metals that are found in some environments as a result of contamination from wood preservative are high enough to accumulate in plants and animals. Arsenic b ioconcentrates in aquatic organisms (freshwater BCFs 0-17, marine oysters 350).14
Leaching potential and environmental fateStudies on the movement of arsenic-based wood preservatives from poles have found that they move from poles into soil and from the soil into aquatic ecosystems. The degree to which arsenicals leach is strongly dependent on pH. Much more chemical leaches i nto acid water than into neutral or basic water. Therefore, we should expect arsenicals to leach more in environments high in soil humic acids or where acid precipitation has affected the pH of the soil.15
EcotoxicityMany terrestrial animals are more tolerant of arsenic than humans. However, aquatic organisms are sensitive. Bluegills are the most sensitive fish, with a 48-hour LC50 of 0.5 ppm, and channel catfish are the most tolerant, with a 24-hour LC50 of 47.9 ppm. Arsenic produced reproductive impairment of the water flea at concentrations 7% as high as the LC50 and weight loss occurred at 14% the LC50. The water flea is more sensitive to copper than arsenic, but the combined effects of the CCA formulation are sti ll higher.16