‘We have been poisoning ourselves’: has ice analysis revealed the truth about lead?

Analysis of an ice cores taken from the Swiss Alps together with records dating from the time of the Black Death have revealed that there is no "natural" level of lead in the air, researchers have claimed.

Once in the body, lead is known to have harmful impacts on health, from behavioural to neurological, reproductive and cardiovascular effects....
https://www.theguardian.com/environment/2017/may/30/we-have-been-poisoning-ourselves-has-ice-analysis-revealed-the-truth-about-lead