Robert Repetto and Sanjay Baliga quote a number of studies carried out by Indians in India and abroad on the impact of pesticides on the immune system
Research without change
It is indeed strange that public consciousness of the problem in India is almost non-existent. I am reminded of Omar Khayyam's Rubaiyyat -- "Dust into dust and under dust to lie; sans wine, sans singer and sans end" --which, for Indian scientists, can probably be paraphrased into "From journal to journal and under journals to lie; sans purpose, sans change and sans end". But nonetheless, their findings are worthy of attention.
A 1991 study in Delhi found DDT and HCH residues in urban water, soil and fauna. Even though DDT use had been banned for agricultural uses earlier, human breast milk samples showed DDT and HCH levels had not declined substantially over the past decade, and were comparable to levels found in Punjab, an area of intensive farming (A Nair and M K K Pillai, 1992, 'Trends in Ambient Levels of DDT and HCH Residues in Humans and the Environment of Delhi, India', The Science of the Total Environment, 121:145-157).
Pesticides of many chemical classes are immunosuppressive in most laboratory animals (R P Sharma, 1978, 'Environmental Immunotoxicity: An Overview', in I M Asher (ed) Inadvertent Modification of the Immune Response: The Effects of Foods, Drugs and Environmental Contaminants -- Proceedings of the Fourth FDA Science Symposium, US Food and Drug Administration, Maryland; R P Sharma and R S Tomar, 1992, 'Immunotoxicology of Anticholinesterase Agents', in B Ballantyne and T C Marrs, Clinical and Experimental Toxicology of Organophosphates and Carbamates, Butterworth-Heinemann Ltd, Oxford).
Pesticides may render "people more prone to new or existing diseases by causing immunosuppression" (A Bhatia and J Kaur, 1993, 'Recent Advances in Immunomodulatory Effects of Some Chemical Pollutants -- A Review', International Journal of Environmental Studies, 45: 61-70).
Among Indian cotton field workers, pesticide exposure has been found to be associated with chromosome damage (D S Rupa, P P Reddy and O S Reddi, 1991, 'Clastogenic Effect of Pesticides in Peripheral Lymphocytes of Cotton-Field Workers', Mutation Research, 261:177-180); other studies have also shown similar effects (D S Rupa, P Rita, P P Reddy and O S Reddi, 1988, 'Screening of Chromosomal Aberrations and Sister Chromatid Exchanges in Peripheral Lymphocytes of Vegetable Garden Workers', Human Toxicology, 7: 333-336; P Rita, P P Reddy and S V Reddy, 1987, 'Monitoring of Workers Occupationally Exposed to Pesticides in Grape Gardens of Andhra Pradesh', Environment Research, 44: 1-5; R C Sobti, A Krishan and C D Pffafenberger, 1982, 'Cytokinetic and Cytogenetic Effects of Some Agricultural Chemicals on Human Lymphoid Cells in Vitro: Organophosphates', Mutation Research, 102: 89-102).
Chronic bronchitis, asthmas and pneumonitis have been associated with exposure to agricultural and industrial chemicals with high volatility and small mass, like pesticides (S K Rastogi, B N Gupta, T Husain, N Mathur and N Garg, 1989, 'Study of Respiratory Impairments among Pesticide Sprayers in Mango Plantations', American Journal of Industrial Medicine, 16: 59-538).
Among Indian factory workers chronically exposed to several pesticides, blood lymphocyte levels decreased by as much as 66 per cent in a maximally exposed group. But when a group was asked to take time off from work, immune parameters returned to normal within three months. The study concluded that the pesticide "exposure induced deviations...were time related and cessation of exposure or its withdrawal resulted in achieving normal levels" (S A Khan and S A Ali, 1993, 'Assessment of Certain Haemotological Responses of Factory Workers Exposed to Pesticides', Environmental Contamination and Toxicology, 51: 740-747).
Several Indian studies show that malnutrition affects the immune system. Protein-energy malnutrition atrophies the thymus (an immune system organ), reduces the number of mature lymphocytes (especially helper T-cells) and impairs cell-mediated immune responses (R K Chandra, 1992, 'Protein-Energy Malnutrition and Immunological Response', Journal of Nutrition,122:597-600); Vitamin-B malnutrition reduces antibody production and immune surveillance by natural killer cells (A D Kulkarni, F B Rudolph and C T VanBuren, 1994, 'Nucleotide Nutrition Dependent Immunosurveillance: Natural Killer Cell Cytotoxicity, Gamma Interferon Production and Polynuclear Cell Function', in R A Forse, S J Bell, G L Blackburn and L G Kaebbash (ed) Diet, Nutrition and Immunity, CRC Press Inc, Boca Raton, Florida); phagocytic mechanisms are suppressed in anaemic patients because enzymatic reactions that destroy foreign organisms require iron and, as a result, anaemia increases infectious morbidity and mortality (P Bhaskaram, 1988, 'Immunology of Iron-Deficient Subjects', in R K Chandra (ed) Nutrition and Immunology, Alan R Liss Inc., New York)); and, zinc deficiencies also lead to reductions in circulating T-cells, delayed hypersensitivity reactions and reduced enzymatic activity in respiratory burst, a process by which phagocytic cells destroy foreign bacteria in the respiratory passages (A S Prasad, 1993, 'Acquired Zinc Deficiency and Immune Dysfunction in Sickle Cell Anaemia', S Cunningham-Rundles (ed) Nutrient Modulation of the Immune Response, Marcel Dekker Inc., New York).
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