The conversion of DDT to DDE by some anophelines

The metabolism of DDT has been followed in pure lines of laboratory-reared resistant and susceptible anophelines using gas-liquid chromatography. Relatively large amounts of DDE were formed in vivo by susceptible strains of Anopheles stephensi, A. quadrimaculatus and A. gambiae, and by resistant strains of A. stephensi and A. quadrimaculatus. Resistant and susceptible A. albimanus showed no difference in the rate of DDE production. Volatile metabolites of DDT other than DDE were not observed in most of the strains chromatographed. A procedure for the measurement of DDT-dehydrochlorinase in small numbers of mosquitos was devised based on conditions developed for the glutathione-dependent DDT-dehydrochlorinase present in resistant houseflies. This method has shown the enzyme to occur in highest titre in DDT-susceptible A. albimanus and A. stephensi, indicating little or no correlation with resistance to DDT. Major differences in dehydro-chlorination rates and in patterns of resistance between anopheline species have been observed. In A. stephensi, these differences extend to the level of strains.     

DDT, DDE and DDD in Human Milk from South Africa

Human breast milk samples (n = 30) were collected from mothers within the age range of 19-40 years from Thohoyandou area, South Africa. DDT and its metabolites were extracted from the milk samples using diethyl ether. The crude extracts were subjected to column chromatography. The eluates were then evaporated on a stream of nitrogen up to 0.5 mL. One microliter of the cleaned extracts were injected into GC-ECD for selected organochlorine compounds. The sum total of DDT and its metabolites from each village ranged from not detectable for DMS, GNN and THN to 1,930 ng g(-1) fat wt for BDL while SigmaDDE ranged from 1.32 ng g(-1) fat wt for GNN to 2,570 ng g(-1) fat wt for TKD. SigmaDDD ranged from not detectable for GNN to 4,060 ng g(-1) fat wt for MNN. SigmaDDE was the most predominant followed by SigmaDDD and finally SigmaDDT. This was an indication of breakdown of the parent compound, DDT. Some villages namely, Lufule and Budeli, and Maniini and Makhuvha exhibited similar DDT occurrence of 89% in their areas. Other villages, DMS, TLM, and MND and TKD showed a similarity percentage of 82% while others showed similarities of 75% for GNN and MTT, 69% and 65% for MPG and THN respectively. A significant cluster of DDT and its metabolites between the infants' weight range of 2.5-3.9 kg/body wt was observed. Increase in lipid content was followed by a decrease in the sum DDT in the older mothers (27-30). The estimated daily intake varied from 260 to 4,696 ng/g, nd-10,551 ng/g and nd-4,237 ng/g for DDE, DDD and DDT respectively. These values are significantly (p < 0.05) higher than the FAO/WHO acceptable daily intake (ADI) of 20 ng/g. The SigmaDDT was found to decrease with increasing age of the mothers. The observed high levels of DDE compared to DDT indicated chronic exposure of the mothers to DDT, which is metabolised to DDE and retained in the body.     

Serum DDT and DDE Levels in Pregnant Women of Chiapas,Mexico

The authors measured the main ingredients of technical DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl [p,p[icaron]-DDT]) and its principal metabolite, 1,1-dichloro-2,2-bis (p-chlorophenyl)ethylene [p,p[icaron]-DDE]) in serum collected from 52 pregnant women in Tapachula, Chiapas, Mexico in 1998. The median lipid-adjusted serum levels for the women were 676 ng/g p,p[icaron]-DDT (range: 56–23,169 ng/g) and 4,843 ng/g p,p[icaron]-DDE (range: 113–41, 964 ng/g). In regression analysis, serum DDT and DDE increased with age (test for trend, p = .022) but decreased with total lactation (test for trend, p < .001). Residence in a house that had ever been sprayed for malaria control was also related to serum DDT and DDE. This study provides evidence of high-level exposure to DDT and DDE among pregnant women living in Chiapas, Mexico, despite countrywide restrictions on its use at the time.     

Serum DDT and DDE levels in pregnant women of Chiapas, Mexico

The authors measured the main ingredients of technical DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl [p,p'-DDT]) and its principal metabolite, 1,1-dichloro-2,2-bis (p-chlorophenyl)ethylene [p,p'-DDE]) in serum collected from 52 pregnant women in Tapachula, Chiapas, Mexico in 1998. The median lipid-adjusted serum levels for the women were 676 ng/g p,p'-DDT (range: 56-23,169 ng/g) and 4,843 ng/g p,p'-DDE (range: 113-41,964 ng/g). In regression analysis, serum DDT and DDE increased with age (test for trend, p = .022) but decreased with total lactation (test for trend, p < .001). Residence in a house that had ever been sprayed for malaria control was also related to serum DDT and DDE. This study provides evidence of high-level exposure to DDT and DDE among pregnant women living in Chiapas, Mexico, despite countrywide restrictions on its use at the time.