Lichens as indicators of elevated levels of environmental lead in Utah Valley, Utah. [Rhizoplaca melanophthalma]

Utah Valley, Utah is a high elevation mountain valley with a moderate population and a large aged integrated steel mill. Fine particulate pollution (PM{sub 10}) levels in the valley are among the highest din the US, particularly during winter inversion periods. Utah Valley also has high levels of carbon monoxide. The local bureau of air quality monitored ambient air lead in Utah Valley for several years through the 1980s. Values as high as 1.35 g/m{sup 3} were noted from this monitoring. Such levels are 90% of the federal ambient air standard of 1.5 g/m{sup 3}. Lichens have long been recognized as bioindicators for heavy metals. Reports of high concentrations of lead in lichen thalli were common prior to the development and use of unleaded fuels. Since that time, lead concentrations in lichen thalli have generally decreased. Recent studies indicate lichen lead levels from clean air areas in the western US range from 10 to 25 ppm. Studies of the umbilicate saxicolous lichen Rhizoplaca melanophthalma in Utah Valley indicate lead levels between 188 and 200 ppm. Excess lead in Utah Valley likely originates from the steel mill and from the high number of vehicles still using leaded fuels.