Dicofol

CAS number:
115-32-2

Date circular:
12/12/2006

Chemical name: Benzenemethanol, 4-chloro-.alpha.-(4-chlorophenyl)-.alpha.-(trichloromethyl)-

Final regulatory action has been taken for the category: Pesticide

Final regulatory action: The chemical is Banned

Use or uses prohibited by the final regulatory action:

All uses are banned.

Pesticide use or uses that remain allowed:

None

The final regulatory action was based on a risk or hazard evaluation: Yes

Summary of the final regulatory action:

Based on Annex 1.1 of the Ordinance on the Reduction of Risks linked to Chemical products (ORRChem), the manufacture, the placing on the market, the import in a private capacity and the use of dicofol are prohibited. The ban concerns all type of products, including biocides and pesticides.

The reasons for the final regulatory action were relevant to: Human health and environment

Summary of known hazards and risks to human health: Absorption, distribution and excretion: Dicofol may be absorbed through ingestion, inhalation, or skin contact. The p,p'-dicofol isomer, the main component of technical dicofol, is more persistent in the body than the o,p'-isomer. Dicofol is more polar and less persistent in the body than DDT. Excretion occurs primarily via the faeces. Metabolism involves dechlorination and oxidation of the ethanol moiety and hydroxylation of the aromatic rings.

Acute toxicity: Dicofol is moderately toxic to practically nontoxic. Symptoms include nausea, dizziness, weakness, and vomiting from ingestion or respiratory exposure, skin irritation or rash from dermal exposure, and conjunctivitis from eye contact. Poisoning may affect the liver, kidneys, or the central nervous system. It produces stimulation of axonal transmission of nervous signals, believed to be related to inhibition of ATPases in the central nervous system (CNS). Dicofol is stored in fatty tissues.

·LD_{50, oral} (dicofol 80-96% pure): rat 575-960 mg/kg b.w.; mouse 420-675 mg/kg b.w.; rabbit 1810 mg/kg b.w.; guinea pig 1810 mg/kg b.w.; dog 4000 mg/kg b.w.

·LD_{50, dermal} (dicofol 94-96% pure): rat 1000 to 5000 mg/kg b.w.; rabbit 2000 to 5000 mg/kg b.w.

·LC₅₀, _inhalatory (4h): rat 5 mg/litre air

·LD₅₀, _{intraperitoneal}: rat 1150mg/kg b.w.

Chronic toxicity: Chronic studies have been performed with rats, mice and dogs.

Rats, 13-week study: NOAEL 1 mg/kg diet, equal to 0.07 mg/kg b.w./day. Rats, 2-year dietary study, liver growth, enzyme induction, and other changes in the liver, adrenal gland, and urinary bladder observed at doses of 2.5 mg/kg/day and above. In another two-year study a NOAEL of 0.22 mg/kg/day has been determined. Rats, feeding study, 3 months, LD₅₀ 75 mg/kg/day; liver enzyme induction at 75 mg/kg/day and above; decreased body weights, decreased cortisone levels, and toxic changes in the liver, adrenal glands, and kidneys at 25 mg/kg/day.

Mice, 13-week study: NOAEL 10 mg/kg diet, equal to 2.1 mg/kg b.w./day, based on reduced body-weight, liver enlargement, and increased hepatic mixed function oxidase (MFO) activity.

Dogs, 13-week study: NOAEL was 10 mg/kg diet, equal to 0.29 mg/kg b.w./day. Dogs, feeding study, 3 months: 2 out of 12 survived at 25 mg/kg/day. Poisoning symptoms and effects on the liver, heart, and testes were observed at the 7.5 mg/kg/day dose. Dog, one-year dog study: NOAEL 30 mg/kg diet, equal to 0.82 mg/kg b.w./day, based on liver changes and reduced cortisol response to ACTH at 180 mg/kg diet, equal to 5.7 mg/kg b.w./day.

Rats, long-term dermal exposure: toxic effects on the liver. Rabbits, 4-week dermal study: NOAEL 4.1 mg/kg/day.

Carcinogenicity: Not carcinogenic in rats or humans.

Teratogenicity: No adverse effects in rats, mice or rabbits in dietary studies. In gavage studies (rats/ rabbits), a NOAEL embryofetal toxicity of 25 mg/kg/day / 4 mg/kg/day was determined.

Toxicity in humans: Several observations of human toxicity after exposure to dicofol have been described. Symptoms include nausea, dizziness, and vomiting after ingestion or inhalation as well as skin irritation after dermal exposure.

ADI (acceptable daily intake): 0.002 mg/kg/day based on a chronic NOEL in rats of 0.22 mg/kg/day.

RfD (chronic Reference Dose): 0.0004 mg/kg/day based on a chronic NOEL in dogs of 0.12 mg/kg/day.

Summary of known hazards and risks to the environment:

Exposure to the environment:

Calculated half-life for volatilised dicofol in atmosphere is 3.1 days, which indicates possible long-range atmospheric transport. It meets the UN-ECE POP criterion for long-range atmospheric transport. Dicofol may enter surface waters via spray drift and surface run-off. Dicofol is a highly bioaccumulating substance, it may enter the marine environment through migration of organisms and biomagnification.

Dicofol is practically insoluble in water and adsorbs very strongly to soil particles. The degradation of dicofol in soil is moderately slow (DT50 30-60 days) which increases the transportation and biomagnification potential in terrestrial environments.

In watercourses dicofol hydrolyses within a few days in neutral and alkaline waters, but it is quite stable (DT50 value of 47-85 days) in acidic waters with pH 5. The p,p'-isomer is more resistant ot degradation compared to the o,p' isomer. The main hydrolysis products are the corresponding dichlorobenzophenons (DCBP). Estimated properties for solubility, vapour pressure and octanol/water partition coefficient of DCBP are approximately the same as for dicofol. Dicofol therefore meets the criteria for persistency in water, sediment and soil only in water under acidic conditions.

Many studies have shown that dicofol is found in wildlife. The environmental half-life of most biota was between 18 and 39 days.

Toxicity to aquatic organisms:

Dicofol is extremely toxic to aquatic organisms in acute and chronic toxicity tests and may cause long-term adverse effects. The experimentally determined BCF (28-day exposure) in whole fish samples was 10 000.

Acute toxicity data are available for fish, crustaceans, molluscs and algae. The following values have been published:

LC50, fish: 0.12 mg/l; LC50, crustaceans: 0.06 mg/l; LC50, molluscs: 0.015 mg/l; LC50, algae 0.075 mg/l.

NOEC (60d fish early-life-stage test): 4.4 µg/l; NOEC (Daphnia magna) survival and reproduction: 125 µg/l.

Toxicity to birds:

LD50: 265 mg/kg; i.e. slightly toxic to birds. Long-term effects are eggshell thinning, with effects on reproduction. NOAEC for eggshell thinning (ducks, dietary, 126 days): 2.5 ppm.

Two generation study (American kestels): NOAEC for eggshell thinning: 20 mg/kg

Feminisation of male embryos was confirmed by the presence of primordial germ cells in the male gonad. Second generation adult 5 mg/kg females showed significantly greater number of eggs and hatched chicks lost when compared to a second generation control group. Similar results were found in second generation 5 mg/kg males paired with normal females and had a significant number of chicks posthatching. Results of second-generation breeding parameters indicate a negative effect on reproductive behaviour.

Endocrine disruption:

Dicofol is listed as a candidate for endocrine disruptive substances in the OSPAR Strategy with regard to Hazardous Substances.

Date of entry into force of the final regulatory action: 01/08/2005