Agricultural pollution is one of the greatest threats to the world’s drinking water supplies. Agricultural practices are governed by demand and supply; the world needs food crops and there are many pressures on agriculturalists to meet the demands we place upon them.
There are several causes of agricultural pollution and these are mainly the pesticides, herbicides and fertilizers used to enhance the productivity of arable land. These substances which are used to increase yields and diminish loss of crops are leached into the groundwater systems through runoff. Agricultural runoff pollution is one of the major hazards to human health. The water that is allowed back into the water supply is often contaminated by nitrates, minerals and bacteria and if this is not controlled, there is agricultural water pollution, meaning that the runoff from fields contains the harmful substances which contaminate drinking water supplies (groundwater supplies).
You would be forgiven for thinking that such problems only occur in still-developing countries, but this would be a wrong assumption. The US also has many problems associated with agricultural pollutants leaching into the groundwater supplies. For example, if farmers have applied animal manure to their fields over the winter months, the ground freezes and when the ice melts, this runoff is carried into the groundwater supply. Animal manure is not as healthy or green as you may suppose, as it can carry harmful pathogens and bacteria. When these are returned to the groundwater supply they can have profound effects on human health.
These are compounded when vegetables are washed in contaminated water, and the health of both the agricultural workers and members of the public who eat the vegetables is in jeopardy. Even animal manure causes agricultural pollution. Chicken manure may be full of copper nitrate and this is potentially dangerous when it reaches groundwater supplies which are used for drinking.
Farmers cannot control the agricultural pollution causes as, especially during storms, soil erosion will occur and inside the soil which goes into rivers, lakes and streams, will be harmful pollutants. Agricultural soil pollution is one of the biggest threats to the world’s water supplies, as agriculture accounts for the majority of our fresh water usage. The water farmers use on their land will eventually return to groundwater supplies through evaporation, as part of the hydrological cycle, and as it evaporates, the particles of the harmful pollutants which have been introduced into the soil and onto the crops will result in agricultural air pollution. The quality of air will deteriorate as well as the quality of drinking water.
There are several effects of agricultural pollution, the most serious being the damage it can do to human health when agricultural pollutants find their way into the local drinking water supply. Certain compounds can cause cancers, and the lesser ailments caused by eating vegetables washed in polluted water and grown with the use of nitrates are dysentery and diarrhoea as well as the chance of digesting harmful bacteria which have migrated into the water supply from the farmers’ use of animal manure as fertilizer.
The effects of using DDT and arsenic based pesticides and fertilizers are obvious. Clearly both agricultural workers and the general public are at a great risk when such agricultural pollutants find their way into the human food chain either through consumption of contaminated crops or drinking polluted water.
Farmers are able to control Point of Source runoff to a certain extent as they can treat water from a field that is channeled through a pipe into a river or stream. They cannot successfully control Non-Point of Source (NPS) agricultural runoff pollution as occurs during monsoon conditions and other heavy storms. The water will leaves fields from all points and not just through a pipeline. It is this type of runoff that is of grave concern to environmentalists, governments and the general public.
In fact agriculture is both the cause of pollution both to the water supplies and to air pollution, and also a victim of that pollution. If farmers are using chemicals that are harmful to human health on their soil and crops, then these are entering the groundwater supply which those same farmers use to water their crops. The evaporation process in the hydrologic cycle means that rain will fall on fields but that rain is full of agricultural pollutants.
Science needs to come up with ways of producing crops that will not need the traditional pesticides, herbicides and fertilizers which cause water pollution, but still enhance the growth of crops and protect them from insects and disease so that our demand for food crops can still be met. This is the dilemma we and farmers find ourselves in. Sustainable methods of producing food need to be found and adopted as fresh water supplies are becoming more and more scarce.