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The organochlorine pesticides are lipophilic and persistent and tend to accumulate in soils and growing plants. The contamination of growing plants occurs by adhesion of volatile substances from the air to the plant surface and by the migration of contaminants through xylem in inner ascendant transport. Persistent organochlorine pesticides (HCB, alpha,gamma-HCH, pp'DDE, op'DDT, pp'DDT) levels were determined in soils and rye plants. The aims of the study were the monitoring of organochlorine pesticide concentrations and the comparison of these levels among soil, rye straw, and rye grains. Fifty soil samples and 50 rye plant (50 straw and 50 grains) samples were taken. The GLC-ECD chromatographic results indicated the following contamination levels distributed among soil, straw, and grains: HCB (0.7-1.2-0.7 microg.kg(-1)), alpha-HCH (0.6-3.4-1.2 microg.kg(-1)), gamma-HCH (1.8-27.3-4.4 microg.kg(-1)), Sigma-HCH (2.5-30.7-5.6 microg.kg(-1)), pp'DDE (1.0-7.8-5.5 microg.kg(-1)), op'DDT (16.1-20.4-17.0 microg.kg(-1)), pp'DDT (38.0-41.7-49.6 microg.kg(-1)), and Sigma-DDT (54.2-63.2-72.1 microg.kg(-1)). The study verified the presence of organochlorine pesticides in the Mexican agricultural environment and their migration from soil to the growing rye plants. However, DDT has been banned since 1999 for sanitary reasons, and Lindane is applied only in some cases as a seed dresser. The determined organochlorine pesticide levels in rye plants are low, at residual levels that are below Codex Alimentarius Commission maximum residue limits.

Organochlorine pesticides have been used in Mexico in agriculture as a seed dresser, in sanitation, in malaria control programmes and in livestock to combat ectoparasites. The pesticides applied drift to areas where cattle graze and plants grow. Because of their chemical stability, they accumulate in the lipid-rich tissues of the body. In the body, they circulate throughout all compartments and accumulate in adipose fat. The aim was to monitor the organochlorine pesticide levels in bovine muscle fat and kidney fat from cows living in an endemic malaria zone, where the environmental contamination can be suspected as being higher. Two hundred samples (100 muscle fat, 100 kidney fat) were analysed by gas chromatography. From the pesticides, only hexachlorobenzene (HCB), beta-hexachlorocyclohexane (HCH), gamma-HCH, pp'-1.1.1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), op'-DDT and pp'-DDE, were detected frequently and at levels above the detection limits. The HCB mean level was low at 0.009 mg kg(-1) on a fat basis. From the HCH isomers, beta-HCH mean concentration was 0.039 mg kg(-1) and gamma-HCH was 0.025 mg kg(-1) on a fat basis. Among DDTs, pp'-DDT was the major constituent (0.032 mg kg(-1) on a fat basis) followed by pp'-DDE (0.025 mg kg(-1) on a fat basis) and op'-DDT (0.023 mg kg(-1) on a fat basis). The DDT total (sigma DDT) level was 0.067 mg kg(-1) on a fat basis. Comparing the previous study (1994) and the present one (2002-03), organochlorine pesticide levels were decreased. HCB decreased 3.7 times from 0.033 to 0.009 mg kg(-1) on a fat basis; beta-HCH decreased 3.8 times from 0.149 to 0.039 mg kg(-1) on a fat basis; pp'-DDE did not reveal a significant difference at 0.026 versus 0.025 mg kg(-1) on a fat basis. However, pp'-DDT decreased substantially, 6.7 times from 0.215 to 0.032 mg kg(-1) on a fat basis. The DDT total decreased 3.5 times from 0.236 to 0.067 mg kg(-1) on a fat basis. The tendency for reduced concentrations in organochlorine pesticide levels in Mexican cows is caused by their substitution with pyrethroids used in agriculture and by the Mexican Ministry of Health in sanitary programmes.

Organochlorine pesticides, due to their persistence, accumulate in food chains and cause elevated contamination in human beings. These residues bioconcentrate in lipid-rich tissues according to the equilibrium pattern of internal transport and lipid tissue content. The analyses of maternal adipose tissue, maternal blood serum, umbilical blood serum, colostrum, and mature milk indicate circulation of these compounds through all compartments of the maternal body, including their crossover of the placental barrier. The greatest residue levels found correspond to DDTs, with highest levels determined in colostrum (5.71 mg/kg of DDT total), followed by adipose tissue with 5.66 mg/kg and in mature milk with 4.70 mg/kg. Among DDTs, pp'DDE is the most predominant compound. The paired analyses of organochlorine pesticide residue levels between mother blood serum and umbilical blood serum demonstrate significant correlation and their transfer from mother to fetus through the placenta. The paired analyses of adipose tissue and colostrum and mature milk contamination levels indicate a high degree of coherence, principally of DDT, in the body and lactation as a decontamination means.

Concentrations of organochlorine insecticide residues such as DDT, DDE, gamma- and beta-HCH were determined in human adipose tissue samples obtained during autopsies from urban and suburban areas of Veracruz city, the state of Veracruz and out-of-state areas, collected during 1988 and 1991. The mean levels of total DDT, which constitutes the predominant accumulated pesticide, decreased from 17.45 mg/kg in 1988 to 14.06 mg/kg in 1991. The highest levels of total DDT were determined in persons from suburban areas of Veracruz city and among persons over 51 years old with the highest levels of contamination observed in patients dying of cardiovascular disorders.

This monitoring study of 192 samples of cow's milk collected from the central region of Veracruz state was conducted to determine the contamination levels of organochlorine pesticides. The results obtained for mean DDT and HCH levels were 0.057 and 0.098 mg/kg respectively expressed on fat basis and are within FAO tolerances and similar to those found in other tropical countries.