Lindane

Lindane is an insecticide. It can be used to kill insects. The European Union allows its use as an insecticide since 2008. This is because it takes a very long time to decay. Checks are now getting done to see how bad to humans it really is. It can cause diseases such as Cancer or Parkinson's disease. 
The World Health Organization classifies Lindane as "Moderately Hazardous". International trade with it is restricted and regulated under the Rotterdam Convention on Prior Informed Consent. Over 50 countries have banned it. It might be included in Stockholm Convention on persistent organic pollutants. This would make it illegal to produce or use it all over the world.