Pesticides have been one of the main chemical products most used in the agricultural industry due to their high efficiency in eliminating insect pests, pathogens and even increasing plant production. However, the negative effects are greater than the positive ones, since their use brings with it consequences for the environment and human health. The presence of pesticides through non-dietary intake of contaminated soil and dust exceeds the permissible limits set by the WHO and the Food and Agriculture Organization of the United Nations.
Risks to the environment and soils from pesticides
Pesticides contain complex substances of chemical origin that help maintain crops, however, their negative effects outweigh the positive ones. The production of these products increased at the beginning of the 20th century as part of the oil industry, being one of the most manufactured and used chemical products today by large companies.
Pesticide contamination in the area where they are applied occurs in a short period of time, causing immediate contamination of the abiotic environment (soil, air, surface and ground water), in addition to the death of insects, annelids, and other beneficial organisms in the area. When they are applied and fall to the ground, they are dragged or leached into ground and surface water, reaching water reservoirs for human consumption, to later evaporate into the air and circulate great distances in warm climates and concentrate in cold areas. Even these compounds, when found in dust on the ground, the particles can be inhaled and easily adhere to the skin, mucous membranes, food, and others. (1).
Pesticides not only combat pests but also soil microorganisms. These microorganisms allow gas exchange and water entry, thus keeping the soil fertile.
Likewise, pesticides when they reach the soil act depending on soil variables such as: humidity, temperature, organic matter, type of clay, pH, soil ion exchange and physicochemical characteristics. However, the colloidal fraction of the soil will be the one that will have the greatest ease of retention of pesticide molecules, making their degradation almost impossible. This colloidal fraction is made up of part organic matter and part inorganic matter (clay minerals), which helps us to know the absorption and inactivation margin of a pesticide, in addition to the fact that it has been shown that the most frequently used pesticides (chlorinated, phosphorous, carbamates), the phosphorous ones are considered the most strongly inactivated in the soil, in minerals and in organic soils; because they are the most easily adsorbed by the soil. (2).
An important aspect of these chemicals is that they have a high affinity for fats (lipids), which makes them bioaccumulative in the tissues of living beings. When they reach the soil, they accumulate in organic matter and remain in the soil for years. Even some types of plants, such as cucurbits (pumpkin, cucumber or watermelon), absorb these pesticides from the soil, resulting in contamination. In crops such as potatoes and strawberries, alarmingly high amounts of organophosphates, dithiocarbamates and carbamates have been found, among which the presence of some endocrine disruptors such as carbofuran, chlorpyrifos, diazinon, mancozeb and methomyl was detected. In addition to detecting atrazine, which is one of the most commonly detected pesticides in soil, surface waters, as well as in drinking water, and has become an object of constant concern due to its endocrine capacity and carcinogenic activity. (3).
“Exposure to pesticides is commonly caused by the consumption of six important crops: wheat, rice, tomatoes, apples, potatoes, corn and lettuce. But the direct damage is to the day laborers.” (Ortiz.2014)
Human exposure to pesticides occurs through the consumption of fruits and vegetables from poisoned crops or from animals grazing in contaminated areas. The most affected population near crops that use pesticides is the children , because children play on the floor and often put objects and hands in their mouths. Being considered endocrine disruptors, carcinogens and neurotoxins, these compounds also remain for long periods, they are known as persistent organic pollutants (POP).
Types of pesticides
- Algaecides: They delay the growth or appearance of algae.
- Antimicrobials: They kill plant germs and microbes (bacteria and viruses).
- Desiccants: They cause water loss, thus drying out plant-based pests.
- Defoliants: They cause certain plant species to lose their leaves, preventing them from photosynthesizing.
- Bug bombs: They kill insects. They are applied from airplanes or drones and create a kind of mist over the crop.
- Herbicides: They kill the grasses or plant species that proliferate in the cultivated areas, leaving only the agricultural species.
- Molluscicides: They cause slugs and other mollusks to dry out.
- Insect growth regulators: They inhibit certain steps in the reproductive circuit of insects.
- Rodenticides: They kill mice, rats, corn cobs and other rodents.
- Antifungals or fungicides: They prevent the appearance of fungi or eliminate them from fruits and plants.
- Repellents: They cover protected species and give them an unpleasant smell and taste that drives away unwanted insects.
- Synergistic pesticides: They enhance and maximize the effectiveness of other pesticides.
Like pesticides, they are classified as: low hazard, toxic, harmful and extremely toxic. (4)
Pesticide residues in drinking water and in the aquatic ecosystem.
Water quality has been deteriorating over the years due to the use of pesticides. This happens when the chemicals filter into the soil and reach the groundwater, contaminating rivers, lakes and finally even the oceans. The pollution is generated by nitrate, which in excess in the water causes the formation of nitrates. eutrophication , which is the accelerated growth of phytoplankton and other aquatic species, causing an imbalance in the ecosystem. On the other hand, if the concentration of an individual pesticide exceeds the value of 0.1 µg/L and the total exceeds 0.5 µg/L, the water is not suitable for human consumption.
When the water carries the chemicals, just like the wind, they erode the soil. In addition, some farmers, after applying the pesticides, wash the containers or tools they used in nearby lakes, dams or rivers. This causes great ecological damage, directly affecting fish, birds, mammals and human health; in the fishing industry, it is estimated that six to four million contaminated fish are eliminated per year. However, the damage to health caused by the consumption of contaminated fish and shrimp increases year by year.
“It is noted that the increased rates of disease, deformities and tumours in commercial fish species from heavily polluted areas of the North Sea and UK coastal waters since the 1970s are consistent with documented effects of pesticide exposure.” (WWF, 1997).
Pesticides in Mexico
In Mexico, the agencies that regulate pesticides are the Ministry of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA) and the Ministry of Health (SSA). At the international level, the Food and Agriculture Organization of the United Nations (FAO) is an organization that has directed efforts for the proper management of pesticides. On the other hand, the FAO recorded that the annual consumption in Mexico is 35 thousand tons of pesticides. In 2009, Mexico was the largest consumer (36.3 thousand tons) of pesticides, followed by Japan, India and Turkey.
Pesticides have been deliberately added to the environment, causing serious effects on this medium. The organisms that make up the biosphere are seriously threatened by the excessive use of pesticides. The creation of these products was in order to provide enough food for humans, however, in contrast, they are promoting diseases and causing negative effects. Therefore, more natural and sustainable forms of crop protection are being promoted without the need to affect bird, fish and other animal populations, in addition to avoiding irreversible contamination of soil, water and air.
What do you think about pesticides? What other techniques would you implement to replace the use of pesticides, fungicides, among others?
To read the article with videos, visit the following link. (25) Pesticides: death of SOILS and contamination in WATER (STAGE I) | LinkedIn