Agrochemicals and their effects

Agrochemicals are the chemical inputs used to manage farming and livestock — fertilisers, liming and acidifying agents, soil conditioners, pesticides, and animal-husbandry chemicals such as antibiotics and hormones — and while they raise short-term productivity, their overuse carries substantial environmental cost. Excess fertiliser and pesticide application contaminates groundwater, making it non-potable, and disturbs soil fertility; because most chemical fertilisers supply nitrogen, phosphorus and potassium in varying ratios, imbalanced use shifts soil acidity, which in turn affects soil microbial communities, greenhouse-gas flux from the soil and the bio-availability of key nutrients, eventually making soil too acidic or alkaline for healthy plant growth. Persistent synthetic residues such as DDT and PCBs compound this by causing further nutrient and pH imbalance and reducing the quality of agricultural produce — a problem the chapter frames as addressable chiefly through a shift to sustainable agriculture. On human health, pesticide exposure is linked to brain and blood cancers, neurotoxicity, Parkinson's-like symptoms, infertility, birth defects and reproductive/behavioural disorders; nitrates leached from fertilisers interact with haemoglobin to form methaemoglobin, reducing the blood's oxygen-carrying capacity and causing Blue Baby Syndrome (cyanosis) and hypoxia, while also vasodilating blood vessels and lowering blood pressure. A further, ecosystem-wide risk is biomagnification: pollutan …