Lead pollution approaches natural background levels

Humans have a 3,500-year history of emitting neurotoxic lead into the atmosphere from mining, using leaded gasoline, and other activities. But efforts in the past several decades to reduce lead emissions have worked well, confirms a study of peat bogs in northern Alberta (Geophys. Res. Lett. 2016, DOI: 10.1002/2016gl070952). A team led by William Shotyk of the University of Alberta extracted peat cores from six sites to assess lead deposited from the atmosphere. The team tested samples from various core depths for lead and also for thorium, which is an indicator of general mineral abundance, and dated the samples using ¹⁴C and ²¹⁰Pb methods. Depending on location, the researchers found, lead amounts peaked from 1960 to 1995 as the use of leaded gasoline in on-road vehicles was eliminated in the U.S. and Canada and other lead controls were implemented. Strikingly, the surface layers of the Alberta cores showed lead amounts comparable to samples taken from a Swiss bog and dated to 6,000 to 9,000 years ago, which can be considered natural background levels. “The lack of contemporary lead contamination in the Alberta bogs is testimony to successful international efforts of the past decades to reduce anthropogenic emissions,” the researchers say.