Synthetic pesticides like DDT were widely used in the 1940's, but banned by 1972 in the US for it's harm to the environment. Apparently, bald eagles and falcons suffered the most from DDT.
But DDT was also blamed for a significant number of preterm human births. Even though DDT is banned in the US, many underdeveloped countries that grow food for the US still use it.
Dursban is another nasty synthetic pesticide that was banned in the US in 2000 for causing nervous system failures later in life to children that were exposed to it. However, in a strange irony, there are a few US manufacturers that are allowed to produce it only for foreign crops. Usually, it's the nervous system, endocrine or the reproductive system that is hurt by synthetic pesticides.
There are at least 160 synthetic pesticides that are also classed as possible carcinogens. Crazy thing is that most bugs develop resistance to these pesticides and so in many countries, more is applied, solutions are mixed or more toxic ingredients are added. A lesser of the evils is botanical pesticides.
These are toxic substances naturally extracted from plants and less harmful to the environment, humans and animals. Neem, Limonene and Capsaicin are examples of these types of pesticides. One drawback is that since they are less toxic, they usually haved to be applied more frequently. There are a few botanical pesticides that are considered toxic to humans and animals, like Rotenone and Nicotine. These adversely affect the central nervous system as a poison.
Organic pesticides are strong smelling essential oils from cedar, cinnamon, citrus, citronella and clove. Other organic pesticide oils not beginning with the letter "C" are garlic, peppermint and rosemary. These organic oils work by disrupting the insect neurotransmitters. Thankfully, these neurotransmitters are not present in humans and animals, so they are considered safer than most other pesticides. The solutions work quickly, but they don't last very long, maybe a month.