Welcome back! Today we explore why pollution caused by human synthesised chemicals used in agriculture are so widespread.

The key property that these chemicals possess is their PERSISTENCE.

They are usually very stable organic compounds, especially since most of them are halogenated. They do not degrade easily, lasting in the environment for very long periods of time, even up to a few decades. This persistence is also determined by the surrounding environment and climate, where the pesticides persist 3-8 times longer in cold climates compared to temperate ones. Such chemicals contaminate the air, soil and groundwater.

Hence, when such pesticides are applied, they tend to have widespread and prolonged effect on all the humans, wildlife and organisms. At the target site, the pesticides may enter the surface waters or volatilise into air after being sprayed. The excess pesticides applied onto the crops may also leak into groundwater sources. From the surface waters, the pesticides may reach the aquatic organisms, including those in the sediments. From the air, the pesticides may also get deposited onto the soil.

Due to their persistence, the pesticides are able to see through many different stages of natural environment processes to contaminate and remain in air, soil and water sources.

This is a compressed summary, to find out more, head to this link https://www.who.int/ceh/capacity/Pesticides.pdf provided by the World Health Organization.