Residues of DDT and HCH in wheat samples collected from different states of India and their dietary exposure: A multicentre study.

Under a multicentre study conducted by the Indian Council of Medical Research, 1712 samples of wheat grain/flour were collected from urban and rural areas in 11 states representing different geographical regions of India. These samples were analysed for residues of DDT (2,2-bis (p-chlorophenyl)-1,1,1-trichloro ethane) and different isomers of HCH (1,2,3,4,5,6-hexachloro cyclohexane, a mixture of isomers) by gas-liquid chromatography. Residues of DDT were detected in 59.4% of 1080 samples of wheat grain and in 78.2% of 632 samples of wheat flour. Different isomers of HCH were present in about 45-80% of the samples of wheat grain/flour. Medians of DDT and total HCH, respectively, for pooled samples of wheat grain were 0.013 and 0.035 mg kg(-1), while those for wheat flour were 0.01 and 0.02 mg kg(-1). Estimated daily intakes of DDT and different isomers of HCH through the consumption of wheat contaminated at their median and 90th percentiles constituted a small proportion of their acceptable daily intakes. Amongst the pesticide residues analysed, statutory maximum residue limits have been fixed only for gamma-HCH in wheat in India, as 0.1 mg kg(-1) in wheat grain and zero in wheat flour. Residue levels of gamma-HCH exceeded these maximum residue limits in five of 1080 samples of wheat grain and in 340 of 632 samples of wheat flour. The failure to meet the requirement of the gamma-HCH maximum residue limit in large number of wheat flour samples was attributed to the fixation of practically unachievable zero limit. Comparing the previous studies and the present one, the levels of residues of DDT and HCH in wheat were significantly decreased.

Estimation of residues of carbofuran and its metabolites in sugarcane and soil by derivatization with 1-fluoro-2,4-dinitrobenzene and gas chromatography with nitrogen-phosphorus detection.

Residues of carbofuran and its metabolites were studied in sugarcane plants and soil after application at 1 and 2 kg/ha. The residues of carbofuran and its metabolites were extracted by refluxing with 0.25N HCI, partitioned into dichloromethane, and cleaned up on acidic alumina. The respective 7-phenols of carbofuran, 3-ketocarbofuran, and 3-hydroxycarbofuran were destroyed by treatment with ceric ammonium sulfate, and the residues were derivatized with 1-fluoro-2,4-dinitrobenzene. The derivatives were estimated by gas chromatography with nitrogen-phosphorus detection. The concentration of 3-hydroxycarbofuran in sugarcane plants remained higher and persisted longer than that of the parent compound. Carbofuran-derived residues were not detected in cane juice. Soil samples were found to contain only carbofuran, which declined at a very fast rate that followed a first-order kinetics rate of reaction.

DDT and HCH residues in dairy milk samples collected from different geographical regions of India: a multicentre study.

Under a multicentre study conducted by the Indian Council of Medical Research, 2205 samples of dairy milk were collected from rural and urban areas of 12 states representing different geographical regions of India. These samples were analysed for residues of DDT and different isomers of HCH by gas-liquid chromatography. Analytical quality assurance between various participating laboratories was ensured through analysis of check samples. The residues of DDT and HCH were detected in more than 80% of samples analysed. Concentrations of DDT residues, alpha-HCH, beta-HCH, gamma-HCH and delta-HCH exceeded their maximum residue limits prescribed by the Ministry of Health and Family Welfare of the Indian Government in 37, 21, 42, 28 and 4% of the samples, respectively. Median values of DDT and HCH found in dairy milk in India were more than the corresponding values reported from most other countries. The results showed significant variations in the incidence as well as level of these contaminants in dairy milk from different regions of the country.

Organochlorine pesticide residues in human milk in Punjab, India.

Human milk samples collected from areas having intensive cotton cultivation and sparse cotton cultivation in Punjab (India) were analysed for organochlorine insecticides. Both DDT and HCH were detected in almost all the samples analysed. The average levels of Sigma-DDT and Sigma-HCH residues in samples from cotton-growing areas were significantly higher than in those from areas where cotton is sparsely grown. Residues of Sigma-DDT mainly comprised p,p'-DDT and p,p'-DDE, while those of Sigma-HCH residues were mainly in the form of its beta-isomer. Median values of 0.52 microg g(-1) of Sigma-DDT and 0.19 microg g(-1) of Sigma-HCH in samples of human milk from cotton-growing areas of Punjab (India) were higher than those reported from most other countries in the World.

Contamination of bovine (buffalo, Bubalus bubalis (L.)) milk from indoor use of DDT and HCH in malaria control programmes.

Samples of bovine (Buffalo, Bubalus bubalis (L.)) milk collected from randomly selected houses of Ludhiana and Sangrur districts of Punjab, India, where DDT and HCH, respectively, had been sprayed for the control of malaria, were analysed for insecticide residues between September 1985 and June 1986. The average concentration of DDT residues in samples from the DDT sprayed area were approximately 4-12 times higher than those in the corresponding samples from HCH sprayed areas. Mean levels of HCH residues in samples from the HCH sprayed area were greater than those in samples from DDT sprayed areas by factors of 2-11. Milk samples collected from four rural houses in each district before and after applications of DDT or HCH for mosquito control also showed that indoor use of these insecticides results in a substantial increase in residue levels. About 74% of the samples analysed contained DDT residues above the extraneous residue limit of 0.05 mgkg-1 (whole milk basis). Estimated maximum daily intakes of DDT and beta-HCH through consumption of contaminated milk by 1-3-year-old children exceeded their acceptable daily intakes by nearly three and five times, respectively.

Contamination of stored food and feed commodities from indoor use of HCH and DDT in malaria control programmes.

Samples of wheat grain, straw, flour and green fodder taken from houses sprayed with either HCH or DDT for mosquito control showed the presence of HCH residues at concentrations of up to 91.2, 208.8, 33.1 and 459.0 mg kg-1 and DDT residues up to 11.3, 86.1, 2.2 and 5.4 mg kg-1, respectively. The mean level of HCH residues in samples of wheat grain collected from randomly selected houses in areas sprayed with HCH for the control of malaria was approximately 8 times higher than that for corresponding samples from DDT sprayed areas. In contrast, DDT residues in wheat grain samples from the DDT sprayed area were 3 times higher than the samples from the HCH sprayed area. The results suggest that significant amounts of residues of HCH and DDT become transferred to commodities stored in houses sprayed with these insecticides for mosquito control.

Occurrence of DDT and BHC residues in human milk in India.

PIP: The presence of pesticide residue of DDT and of BHC were determined in 1979 in samples of milk from 75 lactating mothers from Punjab, within a week after delivery. DDT and BHC residues were found present in all 75 samples collected. Recovery of isomers of BHC and metabolites/isomers of p.p'-DDT from the spiked samples was above 80%. The mean level of DDT residue was 0.51 ppm, which is more than the level reported from the U.S., Canada, Europe and Australia, but less than the level found in Guatemala. BHC residues also were higher than those found in other countries, with the exception of Japan. DDT level of 0.5 ppm in milk represents an infant intake of 0.09 mg/kg/day, which is 18 times the acceptable daily intake (0.005 mg/kg/day) recommended by the WHO. Acceptable daily intake of BHC has not yet been established.^ieng

Simplified method for estimation of DDT and hexachlorocyclohexane residues in milk.

A procedure that combines acetone-hexane extraction and cleanup by treatment with concentrated sulfuric acid is described for determining DDT and 1,2,3,4,5,6-hexachlorocyclohexane (HCH) residues in milk. Recoveries from samples fortified with 0.004-0.008 ppm of different HCH isomers and 0.01-0.02 ppm DDT and its metabolites ranged from 83.4 to 99.8%. The proposed method is simple and rapid, and does not require the use of costly adsorbents.

Contamination of bovine milk with DDT and HCH residues in relation to their usage in malaria control programme.

The contribution of spraying DDT and HCH for malaria control towards the contamination of bovine milk was investigated by analysing milk samples collected from preselected localities sprayed with either DDT or HCH in the Punjab. A direct correlation was found between the amounts of residues of these insecticides in milk and their typical usage pattern for the mosquito control programme. It is considered that these results may have significant bearing on the regulatory control of DDT and HCH residues in milk.

DDT residues in butter and infant formula in India, 1977.

Samples of commercial brands of butter and infant formula from different parts of India were examined for DDT residues. All 18 samples of butter representing nine brands were contaminated. Levels of DDT residues ranged from 0.42 to 11.36 ppm and exceeded the Food and Agriculture Organization/World Health Organization practical residue limit of 1.25 ppm in 90 percent of the samples. All four brands of infant formula contained DDT residues above the practical residue limit. Most DDT residues were in the form of p,p-TDE in both commodities. This contamination of milk with excessive amounts of DDT residues seems to be widespread in India.

Studies on the mechanism of DDT resistance in Culex pipiens fatigans. Lipids of susceptible and resistant strains.

The mechanism of DDT resistance in Culex pipiens fatigans is poorly understood. Earlier studies indicated that the dehydrochlorination of DDT does not explain resistance in this species. Studies on the role of lipids as a mechanism of resistance included the estimation of lipid content and the determination of the proportions of different classes of lipids in the larvae of susceptible and resistant strains. There was no evidence of any correlation between the lipid content and DDT resistance in this species and the proportions of neutral lipids, phospholipids and fatty acids of different strains did not indicate any consistent correlation with DDT resistance.Within one strain, the larvae containing the higher amount of lipids were able to resist better the toxic effect of DDT. Analysis of fatty acids of the larvae that survived and died as a result of treatment with DDT did not reveal any difference.Neither p,p'-DDT nor o,p'-DDT at sublethal concentration affected the lipids of the larvae of susceptible and resistant strains.