Heptachlor

Synonyms and Trade Names (partial list): Aahepta, Agroceres, Baskalor, Drinox, Drinox H-34, Heptachlorane, Heptagran, Heptagranox, Heptamak, Heptamul, Heptasol, Heptox, Soleptax, Rhodiachlor, Veliscol 104, Veliscol heptachlor.
Appearance: White to light tan, waxy solid or crystals with a camphor-like odour.

Overview

Heptachlor is a non-systemic stomach and contact insecticide, used primarily against soil insects and termites. It has also been used against cotton insects, grasshoppers, some crop pests and to combat malaria. Heptachlor is highly insoluble in water and is soluble in organic solvents. It is quite volatile and can be expected to partition into the atmosphere as a result. It binds readily to aquatic sediments and bioconcentrates in the fat of living organisms. Heptachlor is metabolised in animals to heptachlor epoxide, whose toxicity is similar to that of heptachlor, and which may also be stored in animal fat.

The use of heptachlor has been banned in Cyprus, Ecuador, the EU, Portugal, Singapore, Sweden, Switzerland and Turkey. Its use is severely restricted in Argentina, Israel, Austria, Canada, Czechoslovakia, Denmark, Finland, Japan, New Zealand, Philippines, USA and USSR.

Usage in South East Asia

 

Used or Found in Country?

Years of Usage

Regulatory Controls

Cambodia

   

Banned

Lao PDR

Yes

Present

Banned in 1992

Malaysia

Yes

1980- 1989

Banned in 1990

Thailand

Yes

1959

Banned in 1988

Indonesia

   

Never registered for use

Philippines

   

Banned in 1989

Viet Nam

   

Banned in 1992

(table references)

Potential Effects on Humans

There is no information on accidental or suicidal intoxication by heptachlor in humans. 

A study of workers from a plant involved in the production of heptachlor and Endrin found a significant increase in bladder cancer. This result was unexpected as no known bladder carcinogens were used at the plant, however, the small number of deaths (3) makes interpretation of these findings difficult. No deaths from liver or biliary tract cancer were observed, although mortality from cerebrovascular disease was higher than expected. There is limited evidence that cyclodienes such as heptachlor may affect immune responses.

IARC has classified heptachlor as a possible human carcinogen (Group 2B).

Potential Effects on Animals

Symptoms of Heptachlor exposure in animals include tremors and convulsions.

The acute oral LD50 of heptachlor in laboratory animals is in the range of 40 mg/kg body weight in rats to 116 mg/kg in rabbits. Groups of male and female rats were administered daily doses of heptachlor orally beginning at 4 months of age, and continuing for 200 days. All the animals in the 50 and 100 mg/kg groups died by the 10th day of exposure. Three animals in the 5 mg/kg group and 1 in the control died before the end of the study. Beginning on the 50th day to the study, hyper-reflexia, dyspnoea and convulsions were observed in the rats exposed to 5 mg/kg. Histological examination revealed fatty degeneration of the liver cells and moderate fatty infiltration of the epithelium of the renal tubules in the 5 mg/kg exposed group.

In a reproduction study, rats were fed diets containing heptachlor in their diet throughout three generations. Mortality of pups in the 10 mg/kg group was slightly increased during the second and third weeks after birth in the second generation only. No adverse effects were observed in the lower dose levels. WHO has reported no evidence of teratogenicity of heptachlor in rats and rabbits. IARC has concluded that, while there is inadequate evidence for the carcinogenicity of heptachlor in humans, there is sufficient evidence in experimental animals.

Heptachlor has been strongly implicated in the decline of several wild bird populations including Canada Geese and the American Kestrel in the Columbia Basin in the US. A population of Canada Geese at the Umatilla National Wildlife Refuge in Oregon experienced lowered reproductive success and adult mortality. Heptachlor epoxide residues were detected in the brains of dead birds and in the eggs of nests with low success. The reproductive success of American Kestrels in the same area was also reduced. Heptachlor epoxide residues in the eggs were associated with reduced productivity. The presence of residues in the eggs indicates that heptachlor is transferred through the food chain, as Kestrels are not seed eaters, which was the presumed route of exposure for the geese. Concentrations on the treated seeds were lower than the recommended usage level indicating that effects on wildlife may occur, even if heptachlor is used responsibly.

Mink were fed diets containing heptachlor for 28 days, followed by a 7 day recovery period to determine the subacute toxicity of heptachlor to mink. The NOEL for mortality was 50 mg/kg (5.67 mg/kg body weight/day). Signs of toxicity including reduced food consumption and loss of body weight were observed in mink fed the 25 mg/kg diet. In another study, adult male and female mink were fed diets containing heptachlor for 181 days (before and during the reproductive period) to determine effects on reproduction. All the mink fed diets containing 25 µg/g (male and female) died within 88 and 55 days, respectively. The LOAEL, based on reduced kit growth was 6.25 µg/g.

BioAccumulation

The half life of heptachlor in temperate soil is up to 2 years. This persistence, combined with a high partition coefficient (KOW = 4.4-5.5), provides the necessary conditions for heptachlor to bioconcentrate in organisms. Bioconcentration factors of heptachlor and heptachlor epoxide in fathead minnows (Pimephales promelas) were 9,500 and 14,400, respectively. The chemical properties of heptachlor (low water solubility, high stability, and semi-volatility) favour its long range transport, and heptachlor and its epoxide have been detected in Arctic air, water and organisms.

WHO suggests that food is the major source of exposure of heptachlor to the general population.

Heptachlor has been detected in the blood of cattle from both the US and Australia. Heptachlor was detected in 30 of 241 samples in American cattle, and violations of the MRL for heptachlor were detected in 0.02 % of Australian cattle. In both instances, heptachlor was among the most frequently detected organochlorine.

A daily intake of 0.25 µg/person/day (for heptachlor and heptachlor epoxide combined, based on a 60 kg person) was estimated for Vietnam, and of 0.07 µg/person/day (for heptachlor alone) for India.

 

For more information:



Adapted from Persistent Organic Pollutants: Information on POPs, their alternatives and alternative approaches (United Nations Environmental Programme (UNEP) 1995).

Heptachlor Container
Source: FAO
Hatfield Consultants The World Bank funded by the Canadian POPs Trust Fund through the      
Canadian International Development Agency
Not logged on: log on here