Toxicity Caused By Pesticides
Pesticides are widely used on agricultural crops, in the home and yard, and in public places. Pesticides come in a variety of states. They can be solid, such as dusts, granules, pellets, wettable powder, etc. Liquids can be ready-to-use or concentrated. Pesticides can also come as gases such as some of those used for fumigation. To satisfy the growing demand of fruits and vegetables, farmers in the country utilize pesticides to boost production and to prevent insect-pests and diseases, which pose great threats to vegetable and fruit production. It has also been reported that pesticides are commonly used on periodic basis throughout the growing season at very high concentration. Such a use of pesticides during production often leads to the presence of pesticide residues in fruits and vegetables after harvest. In addition, the usage of these chemicals has occasionally been accompanied by serious risks to both human health and the environment because of their toxic potential, high persistence, bio-concentration, and especially, due to their nonspecific toxicity. Some of the pesticides are persistent, and hence, they remain in the body causing long term exposure.
Pesticide Residues: Pesticides residues have been defined as any specified substance in food, agricultural commodities, animal feed, soil, or water, resulting from the use of pesticide. The term includes any derivatives of a pesticide such as conversion products, metabolites, reaction products and impurities that are of toxicological significance.
Monitoring of Pesticide Residues: The aim of pesticide monitoring, is just to ensure that the pesticide residues do not exceed maximum residue level (MRLs) in fruits and vegetables allowed by the government and no misuse of pesticides that could result in unexpected residues in food and that the good agricultural practices (GAP) are being maintained. For monitoring studies in the general survey, all the samples are monitored for residues for all the applied pesticides. The results of these monitoring programmes are used for future development in setting MRLs and risk assessment exercises for public health.
Maximum Residue Limit: To regulate the pesticides residues in food to a safe level, a concept was introduced by Joint FAO/WHO Expert Committee on Food Additives in 1955, and Codex Alimentarius Commission was established in 1964. The maximum residue limit (MRL) is the utmost concentration for a pesticide residue on crop or food commodity resulting from the use of pesticides according to good agricultural practice. The concentration is expressed in milligram of pesticide residues per kilogram of the commodity (mg kg-1/μg g-1/ppm). It should be understood that MRLs are not the safety limits. A food residue can have higher level than MRL but can still be safe for consumption. Safety limits are assessed in comparison with acceptable daily intake (ADI) for short term exposure or acute reference dose.
Pesticides in environment: The environmental impact of pesticides is often greater than what is intended by those who use them. Pesticides can reach a destination other than their target species, including non-target species and contaminate soil, water, turf and other vegetation. Although there can be benefits of using pesticides, but in addition to killing insects and weeds, they can be toxic to a host of other organisms including birds, fish, beneficial insects and non-target plants. Insecticides are generally the most acutely toxic class of pesticides but herbicides can also pose risks to non-target organisms.
Effects of Pesticides: The health effects of pesticides may be acute or delayed in workers who are exposed to pesticides.
Acute effects: A large number of reports are available on acute effects associated with occupational exposure to pesticides. These exposures may be accidental, occupational, or intentional. A review on unintentional pesticide poisoning in 35 countries has been already published. The acute health problems, such as dizziness, headaches, abdominal pain, nausea, vomiting, as well as skin and eye problems, skin conditions, seizures, coma and even death may occur in workers that handle pesticides. Mild to moderate pesticide poisoning mimics intrinsic bronchitis, asthma, and gastroenritis.
Long-term Health Effects
Neurological Problems: Strong evidence links pesticide exposure to worsened neurological outcomes. The risk of developing Parkinson’s disease is 70% greater in those exposed to even low levels of pesticides. People with Parkinson’s were 61% more likely to report direct pesticide application.
Fertility: A number of pesticides like2,4-D and dibromochlorophane has been associated with impaired fertility in males.
Reproductive Effects: Pesticides, lethal to dividing cells of genitalia, may cause
abnormalities in sperms leading to decrease their ability for fertilization. On the other hand, the ova become defective and not able to implant on the uterine surface, leading to early abortion or miscarriages.
Hormone Disruption: Some substances cause physical birth defects and others can cause subtle hormonal effects on the developing fetus or can affect a child’s functional capacities. Hormone disruptors have been linked to many health problems including reproductive cancers. The drug diethylstilbestrol (DES), which was given to pregnant women to prevent miscarriage between 1941 and 1971 worked as an endocrine disrupting chemical on the developing fetus. Decades later, many of these DES exposed daughters developed cervical cancer. Twenty-four pesticides still in the market, including 2, 4-D, lindane and atrazine, are known endocrine-disrupters. Steroid hormones, such as oestrogens, androgens (e.g., testosterone) and progesterone, are crucial for primary sex determination, foetal development and acquisition and maintenance of secondary sexual characteristics in adults. Chemicals, including many pesticides, with similar structures to these hormones can interfere with their function and lead to a variety of developmental and reproductive anomalies.