The US state of California may be leading the battle against harmful emissions, but it is still feeling the effects of past lead contamination.
According to a study by a team from UC Santa Cruz, California, concentrations of environmental lead contamination are continuing to persist in the state. Their paper, printed in the ACS journal Environmental Science & Technology, analysed lead concentration and isotopic composition of both recent and archived samples of the lace lichen. It found that the contamination stretches back to 1892 when lead levels from the northern reach of the San Francisco Bay corresponded to those of high lead emissions from the Selby smelter that were killing horses in adjacent fields at the time.
The authors commented that lead concentrations peaked in 1976 corresponding with the maximum of leaded gasoline emissions in the state. After that, lead concentrations have steadily declined – but isotopic compositions of contemporary samples still correspond with those of previous leaded gasoline emissions in the state.
According to the team, the atmospheric lead now being deposited within the area is from historic emissions of the leaded gasoline that was terminated in the state nearly two decades ago.
