Lead is a toxic metal that was once used regularly in motor fuel, paint, ceramics, glassware, and other consumer products. The phase-out of leaded gasoline significantly reduced vehicle emissions and lead levels in the environment, but it is still used in some aviation fuels and used or produced in a variety of industrial processes. The primary stationary lead sources today are waste incinerators, utilities, lead smelters, and lead-acid battery manufacturers and recyclers. Metal processors, copper smelters. boilers, glass manufacturers, and cement plants also emit lead as part of their operations. Emissions from permitted sources are required to meet federal air quality standards.
Once lead is in the air, it can be inhaled directly, or ingested if the lead particles settle into the soil. Lead emissions from industry are strictly regulated, but legacy lead in paint and soils can still be released into the air.
- If lead-based paint is chipped or disturbed, it can distribute suspended lead particles into the indoor air. For more information about lead-based paint in pre-1978 housing or child-occupied facilities, visit the Lead-Based Paint Program.
- Tetraethyl lead particles from motor vehicles were often deposited along roadways where they bond with soil particles near the road. Although leaded fuel was phased out by 1996, lead previously deposited in soils or sediments can be re-suspended into the air when disturbed.
Air Quality Standards
The Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. Lead is one of the six criteria pollutants regulated under the NAAQS.
In 1978, EPA set the initial emission standards for lead at 1.5 micrograms per cubic meter (µg/m3) in 1978. Twenty years later, EPA strengthened the standards for lead to 0.15µg/m3, ten times stricter that the previous NAAQS.
Based on 2008 emission reports from Utah industrial sources, Kennecott Copper Corporation’s smelter, refinery, power plant, and tailings impoundment near Magna, and its mine and concentrator near Copperton, represent the state’s largest sources of lead. Smaller sources in the state include:
- General aviation aircraft powered by piston-engines that require leaded fuels
- Manufacturing sources
- Industrial, commercial, and utility boilers used by power plants and hot-mix plants.
Point and area sources control lead emissions using bag houses, electrostatic precipitators, and wetting-down areas where fugitive dust emissions are visible.
Air Monitoring for Lead
From 1982 through 2005, the Division of Air Quality (DAQ) monitored for lead in various areas along the Wasatch Front. Utah didn’t exceed the health standard for lead from the late 1970s on, so EPA authorized discontinuation of lead monitoring in the state in 2005. The 2008 revision of the lead NAAQS contained a new standard that required DAQ to again monitor for lead. In January 2010, monitoring was restarted near Kennecott’s smelter and refinery in Magna. DAQ collected air-monitoring data for lead from January 2010 through June 2017. The Division was able to demonstrate to eth EPA that the likelihood of violating the standard was so remote that it was no longer be necessary to run the monitor. With EPA’s concurrence, the Magna lead monitor was shut down in June 2017.
In 2015, DAQ designed and conducted a year-long special study aimed at characterizing the distribution and seasonal trends of hazardous air pollutants (HAPs) such as lead across the Utah and Salt Lake valleys. The study included the installation of two additional air toxics monitors in Lindon and West Valley DAQ observed airborne lead particulate matter (PM10) levels above screening levels at the West Valley, Lindon, and Bountiful monitor sites, but even the highest observed lead concentrations were well below the National Ambient Air Quality Standard (NAAQS) for lead.
Levels above the screening levels were found more frequently in West Valley than the other two sites. While mining and lead smelting activity is generally responsible for the presence of lead in PM10, there was not sufficient data to make a direct connection between the higher lead values in West Valley and current mining activities. The study’s elevated lead concentrations could be the result of lead deposition into the soils from lead smelters operating in the Salt Lake Valley between 1900 and the 1970s.
Lead Concentration Trends
Since 1980, lead concentrations have decreased dramatically both nationally and locally. A gradual phase-out of leaded gasoline for motor vehicles in the 1970s and 1980s accounts for the sharp declines. Air quality trends nationwide show an 82 percent decrease since 2010 in the three-month average of lead emissions. Lead levels in Utah tend to be highest near the state’s largest lead sources.
A trend plot of average annual lead concentrations measured at three monitoring stations in Salt Lake County showed a consistently downward trend for lead emission levels between 1982 and 2005: Monitoring occurred at:
- The former Air Monitoring Center (AMC) at 261 West 500 South, SLC
- Salt Lake County Health Department (SLVHD) at 200 East 610 South, SLC
- Magna at 2935 South 8560 West, Magna.