Use Of Insecticides In Agriculture Research Articles

Permethrin and DDT Resistance in the Malaria Vector Anopheles arabiensis from Eastern Sudan

Assessment of resistance to DDT and permethrin insecticides and molecular detection of knockdown resistance (kdr) alleles were conducted in three populations of Anopheles arabiensis from eastern Sudan. Bioassay mortalities ranged from 96.9% to 99.6% for 4% DDT and from 98.4% to 100% for 1% permethrin. The L1014F and L1014S alleles were detected in 25 of 498 mosquitoes. The overall kdr frequencies ranged from 7.0% in the area where insecticide-treated nets were used to 3.0% in the area with agricultural insecticide use. The presence of the kdr alleles in An. arabiensis in Sudan emphasizes the need to develop appropriate resistance monitoring and management strategies for An. arabiensis.

Best practices for promoting farmers’ health: the case of arsenic history

The most important sources of environmental as well as occupational exposure of man to this metalloid are connected with the mining and smelting of nonferrous metals, the burning of coal for its higher content, the mass use of arsenicals as pesticides, and in both growth stimulators and wood preservatives. The use of arsenical insecticides in agriculture decreased dramatically following the introduction of dichlorodiphenyltrichloroethane (DDT), but the use of arsenical herbicides has increased. Beginning in the 1970s, the use of arsenic compounds, such as for wood preservatives, began to grow. By 1980, in the USA, 70% of arsenic had been consumed for production of wood preservatives. This practice was stopped 4 years ago, due to the US Environmental Protection Agency (EPA) ban of the arsenic- and chromium-based wood preservative chromated copper arsenate. This was, at least in the USA, an example of rational, stepwise risk management, which would mitigate exposure to arsenic for farmers and forestry and wood industry workers. The relatively frequent use of arsenic and its compounds, in both industry and agriculture, points to a wide spectrum of opportunities for human exposure; this exposure can be via inhalation of airborne arsenic, contaminated drinking water, beverages, or from food and drugs. Today, acute arsenic poisonings are mostly accidental. Considerable concern has developed surrounding its delayed effects, for its genotoxic and carcinogenic potential, which has been demonstrated in epidemiological studies and subsequent animal experiments. There is substantial epidemiological evidence for an excessive risk, mostly for skin and lung cancer, among workers exposed to arsenic. Furthermore, the genotoxic and carcinogenic effects have only been observed at relatively high exposure rates. Current epidemiological and experimental studies are trying to elucidate the mechanism for this action, pointing to the question of whether arsenic is actually the true genotoxic or rather an epigenetic carcinogen. Due to the complexity of its effects both options remain plausible. Its interactions with other toxic substances still represent another field of interest.

PYRETHROID AND DDT RESIDUES IN HUMAN BREAST MILK FROM KWAZULU-NATAL, SOUTH AFRICA

ISEE-433 Introduction: In both developing and developed countries, human breast milk remains the best sole nutrient source for infants (especially in the early stages of infancy), even though it could contain pollutants, such as PCBs and DDT. The presence of DDT and other organochlorine compounds in human breast milk has been known for quite some time, from malaria and non-malaria areas. The restriction on or banning of many of these compounds for agriculture in most parts of the world has led to gradual reductions in the levels of organochlorine compounds in breast milk, especially in developed countries. For malaria control however, DDT is still being used in South Africa, although it was interrupted for five years, when pyrethroids were used. Pyrethroids are also being used in significant amounts in agriculture. Aim: We investigated the presence of pyrethroids and DDT in breast milk of women from the northern part of KwaZulu-Natal, that experienced both active malaria control by DDT, and for five years by deltamethrin, and increased agricultural use of insecticides, some of which are pyrethroids. Methods: A total of 152 samples were analysed using GC for the various isomers of DDT, as well as permethrin, cyfluthrin, cypermethrin and deltamethrin. Results: The mothers from Jozini (an active malaria control area) had significantly higher levels of DDT (∑DDT 4.48 mg/kg milk fat) than women from Gwaliweni (∑DDT 1.1 mg/kg milk fat), which served as the reference site. There were, however, no differences between total pyrethroid levels at the two sites (0.647 and 0.211 mg/kg milk fat respectively), and permethrin, rather than deltamethrin made up most of the pyrethroid residues. Multiparae mothers also seemed to have higher pyrethroid levels than primiparae, although this was not significant. Although the Jozini DDT levels were lower than a previous survey done 14 years ago from a comparable town close by (Mseleni, ∑DDT 15.8 mg/kg milk fat), this reduction can be ascribed to the five-year interval with no DDT application, before DDT application was resumed one year before sampling. There is little evidence however, of the deltamethrin applied for malaria control, still being present in breast milk, as only 41% of mothers from Jozini had detectable residues. Conclusion: The pyrethroids that were found are probably derived from agricultural use. This does mean, however, that with pyrethroids being applied, either for malaria control or for agriculture, active ingredients can be transferred to infants' via breast milk, and that the risks posed by the simultaneous presence of DDT and pyrethroids in breast milk should be further investigated.

Prolonged exposure to some agricultural pesticides may increase the risk of lung cancer in agricultural workers

Question Does exposure to agricultural pesticides increase the risk of lung cancer? Study design Cohort study Main results Four of the most commonly used agricultural pesticides (diazinon, dieldrin, metalochlor and pendimethalin) significantly increased the risk of lung cancer in people with the greatest exposure, compared with people who had no exposure (see results table). Three other commonly used pesticides (carbofuran, chlorpyrifos, and dicamba) also increased the risk of lung cancer, but the results were not statistically significant (see results table).There were insufficient numbers of spouses with lung cancer who were directly exposed to specific pesticides to calculate any associated risk. Authors’ conclusions Prolonged exposure to the most commonly used agricultural pesticides increased the risk of lung cancer in farmers and commercial pesticide users. However, this increased risk was only significant for prolonged exposure to diazinon, dieldrin, metalochlor and pendimethalin. It is important to note that the participants in this study were exposed to higher levels for longer periods than the general population, due to their professional, agricultural use of insecticides and herbicides.

Effect Of Permethrin, Pirimiphos Methyl And Bendiocarb On The Osmotic Resistance Of Rat Erythrocytes

Environmental pollution by insecticides is one of the most important problems in the world. Some of the pesticides were found to exert carcinogenic, teratogenic and/or mutagenic effects even following normal agricultural use (U.S.Geological Survey, 1997). On the other hand residues from insecticides, herbicides and insect growth hormones are known to represent the most common food contaminants particularly in developing countries. Thus the wide spread use of insecticides in agriculture stimulated our interest for studying their possible toxic effect(s) in man and animals. The aim of the present work was to study the effect of short term (for 2 weeks) oral daily feeding with diet containing 10 times the human maximum acceptable daily intake (a concentration that may be faced by human) of either permethrin, pirimiphos-methyl or bendiocarb on osmotic fragility of rat erythrocytes. Sprague Dawley male rats were divided into four groups, each consists of 10 animals. Animals of each group were fed either normal diet (control group), permethrin (21.7 ppm), pirimiphos-methyl (4.4 ppm) or bendiocarb (2.0 ppm) for 2 weeks. Twenty four hours later, blood samples were withdrawn and osmotic fragility was determined. The obtained results indicated that permethrin, pirimiphos-methyl and bendiocarb increase the osmotic fragility.

Effect Of Permethrin, Pirimiphos Methyl And Bendiocarb On The Osmotic Resistance Of Rat Erythrocytes

Environmental pollution by insecticides is one of the most important problems in the world. Some of the pesticides were found to exert carcinogenic, teratogenic and/or mutagenic effects even following normal agricultural use (U.S.Geological Survey, 1997). On the other hand residues from insecticides, herbicides and insect growth hormones are known to represent the most common food contaminants particularly in developing countries. Thus the wide spread use of insecticides in agriculture stimulated our interest for studying their possible toxic effect(s) in man and animals. The aim of the present work was to study the effect of short term (for 2 weeks) oral daily feeding with diet containing 10 times the human maximum acceptable daily intake (a concentration that may be faced by human) of either permethrin, pirimiphos-methyl or bendiocarb on osmotic fragility of rat erythrocytes. Sprague Dawley male rats were divided into four groups, each consists of 10 animals. Animals of each group were fed either normal diet (control group), permethrin (21.7 ppm), pirimiphos-methyl (4.4 ppm) or bendiocarb (2.0 ppm) for 2 weeks. Twenty four hours later, blood samples were withdrawn and osmotic fragility was determined. The obtained results indicated that permethrin, pirimiphos-methyl and bendiocarb increase the osmotic fragility.

Agricultural Pesticide Use, Familial Cancer, and Risk of Non-Hodgkin Lymphoma

Abstract To investigate whether the association between agricultural pesticide use and the risk of non-Hodgkin's lymphoma (NHL) is modified by a family history of hematopoietic cancer, including leukemia, myeloma, and lymphoma, we analyzed pooled data on white men from three population-based, case-control studies of NHL conducted in Iowa/Minnesota, Kansas, and Nebraska. Information on the agricultural use of insecticides, fungicides, and herbicides; a family history of cancer; and other risk factors was obtained by interviewing 973 cases and 2,853 controls or, if deceased, their next-of-kin (37% of cases, 43% of controls). The NHL risk was estimated by odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for age, state of residence, type of respondent, and use of hair dye. Compared to men with no family history of cancer, the ORs (95% CIs) of NHL was 1.5 (1.3–1.8) for men with a family history of nonhematopoietic cancer, and 2.7 (1.9–3.7) for those with a history of hematopoietic cancer among first-degree relatives. This positive association was noted for each group of NHL defined according to the Working Formulation, and was most pronounced for small lymphocytic NHL. Among direct respondents, farmers who used pesticides and had a positive family history of cancer or hematopoietic cancer were not at elevated risk of NHL, compared to nonfarmers who had no family cancer history. However, among proxy respondents, ORs were elevated for farmers who had a positive family history of hematopoietic cancer and used animal insecticides (OR = 4.6; 1.9–11.2), crop insecticides (OR = 4.7; 1.6–13.4), or herbicides (OR = 4.9; 1.7–14.2), although the interaction of family history of cancer and agricultural pesticide use was not statistically significant. In summary, the joint effects of the family cancer history and pesticide use were limited to proxy respondents with wide CIs and, thus, provide little evidence that a family history of cancer modifies the association of agricultural exposures with NHL.

Relation between pesticide exposure and intrauterine growth retardation

The increased use of organophosphorus insecticides in agriculture and their widespread existence in the environment poses a potential health hazard. To determine the relationship between exposure to pesticides and intrauterine growth retardation (IUGR), live newborns from singleton pregnancies, with ( n=79) and without ( n=292) IUGR were studied. During the gestational period the mothers were living in agricultural communities in the state of Chihuahua, Mexico. Exposure to agrochemical products was evaluated. A significant association between the history of positive exposure to pesticides (i.e. the women themselves or their newborns who showed acetylcholinesterase activity levels lower than 20%) and the presence of IUGR was found. The proportions of exposure in the cases were 18% and 8% in the control group; the adjusted OR (fat free mass, anti-cytomegalovirus antibodies and placental weight) was 2.33 ( p=0.04).

Comparative Histopathological Evaluation of Permethrin, Pirimiphos Methyl and Bendiocarb Toxicities in Testes, Liver and kidney of rat.

The increasing use of insecticides in agriculture and in public health calls for greater attention for studying their possible toxic effect (s) on man and animals. Acute toxic effects have been relatively well known whereas chronic effects require further studies. The aim of the present work was, therefore, to study the histopathological changes in testes, liver and kidney of rats due to 30 days feeding on diet containing permethrin, pirimiphos methyl and bendiocarb. The dose used for each insecticide represented a concentration that equals ten times the acceptable human daily intake. These doses are far below the LD50, but represent possible exposure doses. Forty male Sprague- Dawley rats were divided into 4 equal groups. Animals of each group were fed either by normal diet, or diet mixed with permethrin (21.739 ppm), pirimiphos methyl (4.350 ppm) or bendiocarb (2ppm) for 30 days. Histological sections of testes, liver and kidneys were examined and histopathological changes and quantitative estimates were recorded. Incidence of spermatogenic suppression, Leydig cell atrophy and vacuolation of Sertoli cells were most prominent in testicular sections from primiphos methyl treated animal testis than in animals of the other groups. Peremethrin feeding resulted in the least deteriorative changes. In sections of liver, dilatation and congestion of blood sinusoids was most evident in the group treated with primiphos methyl and to less extent in those treated with bendiocarb. Swollen hepatocytes with pyknotic nuclei and incidence of apoptosis were also recorded. In kidney sections, vacuolar degeneration, tubular and capsular dilatation, and glomerular congestion were observed especially in primiphos methyl treated rats. In conclusion, the obtained changes were of different severity as a response of exposure to permethrin, pirimiphos methyl or bendiocarb at the same equivelant of human acceptable daily intake.

The role of agricultural use of insecticides in resistance to pyrethroids in Anopheles gambiae s.l. in Burkina Faso.

Agricultural use of insecticides is involved in the selection of resistance to these compounds in field populations of mosquitoes in Burkina Faso. Anopheles gambiae s.l. was resistant to permethrin and DDT in cotton-growing and urban areas, but susceptible in areas with limited insecticide selection pressure (rice fields and control areas). Nevertheless, resistance to these insecticides was observed in a village on the outskirts of the rice fields at the end of the rainy season, suggesting that the latter population of mosquitoes had migrated from the surrounding cotton villages into the rice fields. A seasonal variation of resistance observed in the cotton-growing area is related to the distribution of the molecular M and S forms of An. gambiae, since resistance to pyrethroids has so far only been reported in the S form. Pyrethroid resistance in west African An. gambiae was conferred by target site insensitivity through a knockdown resistance (kdr)-like mutation, which was present at high frequencies in mosquitoes in the cotton-growing and urban areas.

Characterization of P-S Bond Hydrolysis in Organophosphorothioate Pesticides by Organophosphorus Hydrolase

The extensive use of organophosphorothioate insecticides in agriculture has resulted in the risk of environmental contamination with a variety of broadly based neurotoxins that inhibit the acetylcholinesterases of many different animal species. Organophosphorus hydrolase (OPH, EC 3.1.8.1) is a broad-spectrum phosphotriesterase that is capable of detoxifying a variety of organophosphorus neurotoxins by hydrolyzing various phosphorus-ester bonds (P-O, P-F, P-CN, and PS) between the phosphorus center and an electrophilic leaving group. OPH is capable of hydrolyzing the P-X bond of various organophosphorus compounds at quite different catalytic rates: P-O bonds (kcat = 67-5000 s−1), P-F bonds (kcat = 0.01-500 s−1), and P-S bonds s (kcat = 0.0067 to 167 s−1). P-S bond cleavage was readily demonstrated and characterized in these studies by quantifying the released free thiol groups using 5,5′-dithio-bis-2-nitrobenzoic acid or by monitoring an upheld shift of approximately 31 ppm by 31P NMR. A decrease in the toxicity of hydrolyzed products was demonstrated by directly quantifying the loss of inhibition of acetylcholinesterase activity. Phosphorothiolate esters, such as demeton-S, provided noncompetitive inhibition for paraoxon (a P-O triester) hydrolysis, suggesting that the binding of these two different classes of substrates was not identical.

Assessment of location-specific human exposure to dichloro-diphenyl trichloroethane and benzenehexachloride in Gujarat state, India.

On the basis of the use of insecticides in agriculture and vector control programmes, two locations were selected in Gujarat state, India. In location 1 the insecticides are used in both agriculture and vector control programmes while in location 2 they are used only in agriculture. Raw food commodities, water, soil and blood samples were collected from the people residing in these locations, and analysed for total dichloro-diphenyl trichloroethane and total benzenehexachloride residues. Residue levels were significantly lower in location 2 than in location 1.

Insecticide Resistance Issues in Vector-Borne Disease Control

Vector-borne diseases are an increasing cause of death and suffering worldwide. Efforts to control these diseases have been focused on the use of chemical pesticides, but arthropod resistance (whether physiological, biochemical, or behavioral) to pesticides is now an immense practical problem. The pharmacokinetic interactions of pesticides with arthropods, mechanisms of resistance, and the strengths and shortcomings of different resistance test methods are briefly reviewed. Using malaria control as an example, the differences between the efficacy of insecticide-sprayed houses in reducing malaria transmission, and the actual effect of such treatments on vectors are discussed. Reduced malaria transmission as a result of spraying house walls occurs through some combination of killing vectors that land on sprayed walls (insecticidal effect) and by preventing vectors from entering or remaining inside long enough to bite (behavioral effects). Both insecticidal and behavioral effects of insecticides are important, but the relative importance of one versus the other is controversial. Field studies in Africa, India, Brazil, and Mexico provide persuasive evidence for strong behavioral avoidance of DDT by the primary vector species. This avoidance behavior, exhibited when malaria vectors avoid insecticides by not entering or by rapidly exiting sprayed houses, should raise serious questions about the overall value of current physiological and biochemical resistance tests. The continued efficacy of DDT in Africa, India, Brazil, and Mexico, where 69% of all reported cases of malaria occur and where vectors are physiologically resistant to DDT (excluding Brazil), serves as one indicator that repellency is very important in preventing indoor transmission of malaria. This experience with DDT has implications for future control efforts because pyrethroids also stimulate avoidance behaviors in arthropods. Each chemical should be studied early (before broad-scale use) to define types of action against vector species by geographic area, especially for impregnated bed net applications. The problems for vector control created by use of insecticides in agriculture and the potential for management of resistance in both agriculture and vector-borne disease control are discussed.

Faits nouveaux relatifs a l'épidémiologie et au contrôle du paludisme en Afrique tropicale francophone

In French-speaking tropical Africa various investigations have been made which have enabled workers to construct a map of endemicity ranging from the holoendemic area in the Ivory Coast, to hyperendemic areas in Guinea, North Dahomey, and parts of the Ivory Coast, to mesoendemic areas in Haute Volta, Ivory Coast and Cameroun. In most parts transmission varies seasonally, slight at the end of the dry season, vigorous in the rains. P. falciparum is the most common parasite (found in 80–90% of infected persons), and P. malariae is next, either alone or with P. falciparum; P. ovale exists from Liberia to Ghana, Togo, Nigeria and South Cameroun, and its distribution is strictly related to climate. P. vivax does not appear to be present. The vectors are A. gambiae (A and B, and melas) and A. funestus. A. gambiae A has been found resistant to DDT in Haute Volta and the Ivory Coast, and A. funestus to dieldrin in Haute Volta and North Dahomey. The extensive use of insecticides in agriculture is probably responsible for the selection of resistant anophelines. New insecticides are being studied in the region. Chemoprophylaxis, alone or with mosquito control, is regarded as of increasing importance, and experiments are being carried out in many places; resistance to pyrimethamine and proguanil has been found in various areas. Resistance to chloroquine has not been reported. A combination of pyrimethamine and sulphalene has proved as valuable as chloroquine.