The 20th century saw an increase in the use of herbicides to control weeds in agriculture. Some mid-20th century herbicides, like DDT, have been virtually eliminated via international agreements due to high levels of toxicity. However, many legal herbicides are still in use that have serious safety concerns.
Toxicity to Human Placental Cells
In Environmental Health Perspectives, the U.S. National Institute of Health cites a study of the herbicide Roundup by the Laboratoire de Biochimie et Biologie Moleculaire at the Université de Caen in Caen, France. This study found that the active ingredients in Roundup are toxic to human placental cells. In fact, the study found that the particular combination of ingredients in this herbicide is more toxic to human placental cells than the separate ingredients would indicate.
Carcinogenic Effects in Children
In Environmental Health Perspectives, the National Institute of Health published a study by the Occupational Epidemiology Branch of the National Cancer Institute showing that children may be more sensitive to the carcinogenic effects of pesticides than adults. The study showed a higher than expected incidence of cancer in children exposed to pesticides through contaminated food and drinking water, agricultural over-spray and drift, and off-gassing of treated areas.
Human and Animal Poisoning
Herbicides have proven toxic both to people and animals in agricultural settings. According to the World Bank, lack of safety equipment in many industrializing countries has lead to herbicide poisoning of farmers.
The World Bank also cites weed resistance as a problem of increasing herbicide use. As herbicide use increases, weeds develop a resistance that results in increasing herbicide requirements to achieve the same goals.