Pesticides, herbicides, fungicides are all chemical formulations to kills insects, pests, weed, fungi etc. to protect crops, save the yield for our food and supplies. Excessive or abuse of these chemicals is harmful to humans and the environment.
WHO estimates that there are 30 lakh cases of pesticides poisoning and above 2 lakhs deaths each year in the developing countries. Children are particularly vulnerable while they are harmful to developing fetus as well as the mother. Various diseases and disorders are attributed to pesticides, such as cancer, thyroid, diabetes, prostate, obesity, infertility, respiratory disorders and organ failures.
Excessive use of pesticides may lead to adverse impact or destruction of biodiversity killing the flora and fauna. Beyond the local area of spray, pesticides can travel far to other areas through air and water streams. Some pesticides remain in the environment for many years and spread toxicity in future generations.
Sources
http://www.toxipedia.org/display/toxipedia/Effects+of+Pesticides+on+Human+Health
http://www.aljazeera.com/indepth/features/2015/01/cancer-train-india-pesticides-20151411811508148.html