There's no doubt that the risk factors typical of a certain lifestyle which may have a negative impact on human health are numerous, especially considering that research in health (medicine, pharmacology etc) were focused on their determination, but especially on the cause-effect relationship....

Evidence shows that lead-exposed children are more disruptive and have lower achievement. However, we know less about how lead-exposed children affect the learning environment of their classroom peers. We estimate these spillover effects using new data on children's blood lead levels (BLLs)...