п, п'-ДДТ

Описание

DDT is a polychlorinated persistent chemical that exists as a solid under normal conditions.Even though DDT seemed to be a cheap and effective pesticide, enough was known in its early development to raise concerns. DDT is a persistent chemical that lasts a long time in the environment. DDT is fat-soluble and not readily metabolized by higher organisms. Th is meant that DDT accumulated in the fat tissues of higher organisms.

Химические свойства

The technical p,p′-DDT is a waxy solid but in its pure form appears as colourless crystals. It is a mixture of three isomers, namely, p,p′-DDT isomer (about ca. 85%); o,p′-DDT; and o,o′-DDT (in smaller levels). DDT is very soluble in cyclohexanone, dioxane, benzene, xylene, trichloroethylene, dichloromethane, acetone, chloroform, diethyl ether, ethanol, and methanol.

Физические свойства

Whites crystals or waxy solid, with a faint, fragrant, aromatic-like odor. Tasteless. Odor threshold concentration is 200 ppb (quoted, Keith and Walters, 1992) and in water, 350 μg/kg (Sigworth, 1964).

Использование

4,4'-Dichlorodiphenyltrichloroethane is a synthetic organochlorine insecticide. 4,4'-Dichlorodiphenyltrichloroethane functions by opening sodium ion channels in the insects’neurons, causing them to f ire spontaneously which in turn leads to death. 4,4'-Dichlorodiphenyltrichloroethane is banned for agricultural use in North America, it is still commonly used in some countries and particularly as a means of malaria control.

Определение

ChEBI: A chlorophenylethane that is 1,1,1-trichloro-2,2-diphenylethane substituted by additional chloro substituents at positions 4 of the phenyl substituents. It is a commonly used organochlorine insecticide.

Общее описание

Odorless colorless solid. Sinks in water.

Реакции воздуха и воды

Insoluble in water.

Профиль реактивности

4,4'-DDT may react with iron, aluminum, aluminum and iron salts, and alkalis. 4,4'-DDT is incompatible with ferric chloride and aluminum chloride. 4,4'-DDT can also react with strong oxidizing materials. .

Угроза здоровью

Very large doses are followed promptly by vomiting, due to local gastric irritation; delayed emesis or diarrhea may occur. With smaller doses, symptoms usually appear 2-3 hours after ingestion. These include tingling of lips, tongue, and face; malaise, headache, sore throat, fatigue, coarse tremors of neck, head, and eyelids; apprehension, ataxia, and confusion. Convulsions may alternate with periods of coma and partial paralysis. Vital signs are essentially normal, but in severe poisoning the pulse may be irregular and abnormally slow; ventricular fibrillation and sudden death may occur at any time during acute phase. Pulmonary edema usually indicates solvent intoxication.

Контактные аллергены

This insecticide was formerly reported as a sensitizer in farmers or agricultural workers.

Фармаколо?гия

DDT is a nerve poison that affects the sodium channel of nerve membranes. It is a nonsystemic insecticide with contact and stomach action. The most important reactions of DDT (1) are dehydrochlorination to DDE (2) and reductive dechlorination to DDD (3). These reactions occur abiotically, in vivo and in soils. The products resemble DDT in their recalcitrance toward environmental degradation. The stability of DDT and its principal metabolites DDD and DDE, in combination with their lipid solubility and resistance to biological degradation, resulted in their bioconcentration in fish and other organisms exposed to extremely low levels of these compounds in water. Although metabolism of DDT in mammals may proceed via DDD to give 4,4- dichlorodiphenylacetic acid (5), DDE is also formed and stored in fat. It may be slowly depleted by oxidative reactions, and ringhydroxylated derivativeshave been detected in mammals and wildlife samples. Consumption of DDT residues in wildlife and fish by predators resulted in adverse effects.

Токсикология

Although DDT [1,1-(2,2,2-trichloroethylidene)bis(4-chlorobenzene)] has been banned in the United States since 1972, it remains one of the best-known synthetic pesticides. Because DDT is a very nonpolar molecule, it has high lipid solubility. Since DDT is also extremely stable, it accumulates in animal tissues and in the food chain. DDT is still one of the most abundant pesticide residues in food. During the 40 years following DDT s commercial introduction in the 1940s, more than 4 billion pounds were used to control insect-borne diseases. Until 1972, DDT was widely used in the United States, mostly on cotton, peanuts, and soybeans. As a result of its use, DDT residues are now ubiquitous in the environment, and at the present time, some level can be detected in almost all biological and environmental samples. In addition, due to its high lipid solubility, DDT concentrates in milk. When DDT was widely used, levels in human milk and adipose tissue were found to be higher than concentrations permitted in meat and dairy products. However, since its use has been prohibited, storage levels of DDT in human tissue have declined significantly. DDT is, however, still in use in other countries, largely to control insect-borne diseases that pose a substantial threat to public health.

Возможный контакт

DDT is a low-cost broad-spectrum insecticide. However, following an extensive review of health and environmental hazards of the use of DDT, United States Environmental Protection Agency decided to ban further use of DDT in December 1972. This decision was based on several properties of DDT that had been well evidenced : DDT and its metabolites are toxicants with long-term persistence in soil and water ; it is widely dis- persed by erosion, runoff, and volatization ; and the low- water solubility and high lipophilicity of DDT result in concentrated accumulation of DDT in the fat of wildlife and humans which may be hazardous.

Канцерогенность

Dichlorodiphenyltrichloroethane (DDT) is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals.

Экологическая судьба

Biological. In four successive 7-day incubation periods, p,p′-DDT (5 and 10 mg/L) was recalcitrant to degradation in a settled domestic wastewater inoculum (Tabak et al., 1981).
The white rot fungus Phanerochaete chrysosporium degraded p,p′-DDT yielding the following metabolites: 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (p,p′-DDD), 2,2,2- trichloro-1,1-bis(4-chlorophenyl)ethanol (dicofol), 2,2-dichloro-1,1-bis(4-chlorophenyl) e
Mineralization of p,p′-DDT by the white rot fungi Pleurotus ostreatus, Phellinus weirri and Polyporus versicolor was also demonstrated (Bumpus and Aust, 1987). Aerobacter aerogenes degraded p,p′-DDT under aerobic conditions to p,p′-DDD, p,p′-DDE, 1-chloro
Under aerobic conditions, the amoeba Acanthamoeba castellanii (Neff strain ATCC 30.010) degraded p,p′-DDT to p,p′-DDE, p,p′-DDD and dibenzophenone (Pollero and dePollero, 1978).
Incubation of p,p′-DDT with hematin and ammonia gave p,p′-DDD, p,p′-DDE, bis(pchlorophenyl) acetonitrile, 1-chloro-2,2-bis(p-chlorophenyl)ethylene, 4,4′-dichlorobenzophenone and the methyl ester of bis(p-chlorophenyl)acetic acid (Quirke et al., 1979).

Метаболический путь

Upon UV irradiation with methyl oleate, DDT is extensively added to the carbon ? carbon double bond of methyloleate via radical mechanisms. Besides chlorinated stearic acids, several addition products are formed, offering new possibilities to produce bound residues in plants. A mixture of hemin and excess cysteine (the hemin ? cysteine model system) is able to degrade DDT partially and the major degradation products are three water-soluble, non-toxic conjugates of DDT metabolites with cysteine which lose two or three of the five chlorine atoms of DDT. In the presence of a designed 24-residue polypeptide or b-casein, two DDT-binding proteins, an additional fourfold increase in the rate of DDT degradation is observed. Although the concentrations of DDT and cysteine occurring in an organism would be expected to be lower than those in the experiments described, the formation of water-soluble conjugates of DDT with cysteine (and other amino acids) could also play a role in metabolism and excretion of DDT in vivo.

Метаболизм

DDT decomposed very slowly in sunlight, and 93% was recovered unchanged from the surface of an apple after 3 months. DDE decomposed more rapidly than DDT in sunlight. Other reports indicate that DDT was photolyzed under field conditions to give products, including DDE, 4,4- dichlorobenzophenone (6), 4-chlorobenzoyl chloride, 4- chlorobenzoic acid, and 4-chlorophenyl 4-chlorobenzoate. Irradiation of DDT at shorter wavelengths under laboratory conditions gave a variety of products that arose from reactions of photolytically generated radicals.

Перевозки

UN2761 Organochlorine pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Методы очистки

Crystallise DDT from n-propyl alcohol (5mL/g), then dry it in air or an air oven at 50-60o. Alternatively crystallise it from 95% EtOH, and the purity is checked by TLC. [Beilstein 5 III 1833.] TOXIC INSECTICIDE.

Несовместимости

Contact with strong oxidizers may cause fire and explosion hazard. Incompatible with salts of iron or aluminum, and bases. Do not store in iron containers

Утилизация отходов

Incineration has been success- fully used on a large scale for several years; huge incinera- tor equipment with scrubbers to catch HCl, a combustion product, are in use at several facilities, such as Hooker Chemical, Dow Chemical and other producers of chlori- nated hydrocarbon products. One incinerator operates @ 900 C 1400 C with air and steam added which precludes formation of Cl2. A few companies also constructed incinerator-scrubber combinations of smaller size, e.g., a system built by Garver-Davis, Inc., of Cleveland, Ohio, for the Canadian government, can handle 200 500 lb DDT/ day as a kerosene solution. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by follow- ing package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations govern- ing storage, transportation, treatment, and waste disposal.