Arsenic persistence

MetaUic arsenic is stable in dry air, but when exposed to humid air the surface oxidizes, giving a superficial golden bronze tarnish that turns black upon further exposure. The amorphous form is more stable to atmospheric oxidation. Upon heating in air, both forms sublime and the vapor oxidizes to arsenic trioxide [1327-53-3] AS2O2. Although As O represents its crystalline makeup, the oxide is more commonly referred to as arsenic trioxide. A persistent garliclike odor is noted during oxidation. 

After mothproofing wool, the next logical step for Geigy was to invent an insecticide that killed more kinds of pests. Imported natural insecticides made from plants, including pyrethrum from tropical chrysanthemums, rotenone from a tropical vine, and nicotine from tobacco, could be quite expensive they were also not persistent and were easily destroyed by light and heat. American and European attempts to synthesize their active ingredients had failed. Arsenic compounds remained the only cheap and effective insecticides. 

Arsenic vesicants have been thickened with various substances to enhance deployment, increase their persistency, and increase the risk of percutaneous exposure. Thickeners include polyalkyl methacrylates (methyl, ethyl, butyl, isobutyl), polyfvinyl acetate), polystyrene, plexiglas, alloprene, polychlorinated isoprene, nitrocellulose, as well as bleached montan and lignite waxes. Military thickener K125 is a mixture of methyl, ethyl, and butyl polymethacrylates. When thickened, agents become sticky with a consistency similar to honey. Typically, not enough thickener is added to affect either the color or odor of the agent. 

For military purposes, unmodified arsenic vesicants are classified as persistent. However, agent vapors rapidly react with high humidity to lose most of their vesicant properties. Limited solubility slows the hydrolysis of liquid agents. Some hydrolysis products are highly toxic and extremely persistent (see Section 4.4.5). Evaporation rates range from near that of water down to that of light machine oil. 

Arsine is highly volatile and there is little risk of direct residual contamination. However, potential persistent decomposition products include arsenic and arsenic oxides. Wash the remains with soap and water. Pay particular attention to areas where agent may get trapped, such as hair, scalp, pubic areas, fingernails, folds of skin, and wounds. If remains are heavily contaminated with residue, then wash and rinse waste should be contained for proper disposal. Once the remains have been thoroughly decontaminated, no further protective action is necessary. Body fluids removed during the embalming process do not pose any additional risks and should be contained and handled according to established procedures. Use standard burial procedures. 

In addition to the chemicals included on the other lists, the CDC also included heavy metals such as arsenic, lead, and mercury volatile solvents such as benzene, chloroform, and bromoform decomposition products such as dioxins and furans polychlorinated biphenyls (PCBs) flammable industrial gases and liquids such as gasoline and propane explosives and oxidizers and all persistent and nonpersistent pesticides. Agents included in this volume are limited to those that are most likely to pose an acute toxicity hazard. 

Attention focused on inorganic arsenical pesticides after accumulations of arsenic in soils eventually became toxic to several agricultural crops, especially in former orchards and cotton fields. Once toxicity is observed, it persists for several years even if no additional arsenic treatment is made (Woolson 1975). Poor crop growth was associated with bioavailability of arsenic in soils. For example, alfalfa (Medicago sativa) and barley (Hordeum vulgare) grew poorly in soils con-... 

In one study of the persistence of disodium methane arsenic acid in soil, the initial and residual phytotoxicity of disodium methane arsenic acid in soil to cotton was measured over a broad range of concentrations in three soils. Toxicity decreased with time, particularly during the first 16 weeks after soil incorporation. Growth of cotton planted immediately after incorporation of disodium methane arsenic acid in Bosket silt loam was reduced significantly by concentrations of 50-80mg kg-1 in soil. In the same soils, other plants were shown to have different degrees of susceptibility to disodium methane arsenic acid concentrations. Rice was extremely sensitive to soil concentrations of 5ppm, while corn, cotton and wheat were little affected. 

Lewisite (L, 2Cchloroviny Idichloroarsine, 2-chlorovinyl arsonous dichloride) Vesicant — blister agent with Arsenic 30-50 mg/Kg (skin) Highly persistent because of Arsenic in formulation... 

This does not necessarily mean, however, that the risks of lawn care are necessary or inherent to the larger lawn economy. The continued innovation of treatments, after all, is generally hailed by industry as a victory for chemistry that has led to decreased risk. DDT is arguably less hazardous than lead arsenate, or at least more efficient. Discovery of the hazards of DDT led to less persistent chemicals. Glyphosate is likely more benign than 2,4-D, and so on. 

The persistency of brombenzylcyanide vapor in a dugout. U.S. Army Medical Research Laboratory, Edgewood Arsenal, Md. EATR 4065-R1. 1967. 28 p. 

Metals frequently occurring in the state s waste streams include cadmium, chromium, lead, arsenic, zinc, copper, barium, nickel, antimony, beryllium, mercury, vanadium, cobalt, silver, and selenium. These metals are toxic to humans and other organisms, are persistent in the environment, and can bioaccumulate in food chains. They are typically used by businesses in many industrial categories, as shown in Table 2.1-1. 

Temperature, humidity, precipitation, and evaporation are important factors that contribute to the oxidation of sulfide minerals. In warm and wet climates, excessive precipitation may produce persistently high water tables and extensive biological activity that may create reducing conditions in the shallow subsurface and hinder sulfide oxidation (Seal et al., 2002, 208). At the surface, high humidity and temperatures would promote the oxidation of sulfide minerals (Williams, 2001, 274). Frequent precipitation would also suppress evaporation and the formation of arsenic salt deposits (Seal et al., 2002, 208). Furthermore, precipitation and groundwater, which are controlled by climate, are the major sources of water for the production of arsenic-contaminated runoff from sulfide-bearing rock outcrops. 

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