Geospatial Indicators for Risk of Childhood Lead Exposure for California Census Tracts
In June 2020, the California Department of Public Health (CDPH) released a report,
California's Progress in Preventing and Managing Childhood Lead Exposure. An analysis in this report found that 99.3% of California's ZIP codes have at least one geospatial indicator of risk for childhood lead exposure, supporting the development of expanded blood lead testing requirements to ensure all children at risk of elevated blood lead levels receive screening.
Since June 2020, CDPH has been using the data from this analysis to characterize the gradation of geospatial risk factors for lead exposure in California. While the previous analysis aids in informing screening requirements, the map presented here can inform decisions on where to target interventions when resources are scarce. The underlying data is also provided and can be used to assist local health jurisdictions needing to focus on a specific geospatial risk factor for lead exposure relevant to a targeted intervention or outreach effort.
The maps provided below enables a visualization of the distribution of geospatial risk factors for lead exposure throughout the state. Census tract boundaries are driven by population; for this reason, the census tracts of densely populated areas are hard to view on the statewide map and appear black. To address this, zoomed-in maps of three of California's major population centers (the Los Angeles area, the Bay Area, and the Sacramento area) are provided as well.
Areas in the darkest blue are defined as having at least five of the following eight geospatial indicators: high percent of pre-1978 housing; proximity to an air emitter, highway, smelter, small-craft airport, railroad, or speedway; or service by a water district with at least one known lead service line or fitting. The eight indicators included here are only indicative of the potential for soil contamination, water contamination, and lead-based paint. Non-housing sources such as home remedies, imported spices, and jewelry are important sources of lead exposure that are not included in these maps.
The underlying data is available for download below. The data table can be joined to external data sources such as the United States Census Bureau's
American Community Survey or
the Public Health Alliance of Southern California's Healthy Places Index for a more complete picture of the census tracts.
Download the Excel table of underlying data in the maps and metadata.
Map 1: California census tracts by number of geospatial indicators of risk for childhood lead exposure: pre-1978 housing; proximity to an air emitter, state highway, smelter, small-craft airport, railroad, and speedway; and served by at least one known lead water service line or fitting
1 Census tracts with estimated populations of 0 are excluded, leaving 8,012 of California's 8,057 census tracts.A
2 At least 25% of the residential parcels were built before 1978. The American Academy of Pediatrics recommends blood lead testing for children ages 12 to 24 months living in communities where at least 25% of the housing stock was built before 1960.B,
C To acknowledge the risk of lead-based paint in houses built between 1960 and 1978, the criterion was applied using 1978 instead of 1960. A census tract met this criterion if at least 25% of its residential housing, based on Digital Map Product's parcel data from July 2019, was built before 1978.D Residential parcels with a missing year built were included as pre-1978 parcels in these calculations to be protective. Residential parcels with an invalid census tract ID were excluded.
3 Census tract is within 1.7 miles of an air emitter. A list of sites from the US EPA Toxic Release Inventory that emitted lead since 1988 (extracted on August 21, 2019) was mapped and a 1.7 mile buffer was drawn.E The 1.7 mile buffer was chosen in accordance with literature on the lead contamination from two major emitters, Exide and Quemetco.F,
4 Census tract is within 1,000 feet of a state highway. A layer for the California State Highway Network from a December 31, 2017 extraction from the Transportation System Network database maintained by the California Department of Transportation (Caltrans) was used with a 1,000 foot buffer.H The 1,000 foot buffer was determined based on a California Air Resources Board Technical Advisory about air pollution around freeways.I
5 Census tract is within the city of a known current or historic smelter. A list was compiled of the location and activities of iron and steel plants, metal foundries, lead smelters, storage battery manufacturing plants, scrap metal plants, mines that may have mined lead along with zinc, iron, or copper, metal rolling, stamping and metal powder producers, brass and copper smelters, and babbitt and solder manufacturers in California. Some of the texts used were rare and required special handling. Many of the locations were not specific (only the name of the city or town was given) and in two instances, references were only found in older newspapers. Due to the lack of an address and site size for most sites, all census tracts within a city listed as having one of these facilities are included.
6 Census tract is within 1 km of an airport using leaded avgas. Lead continues to be used in avgas for small-craft airplanes. A list of 185 airports where leaded fuel is recorded as being used in the Airport Data and Information Portal from the Federal Aviation Administration (extracted on September 16, 2019) was mapped and a 1 km buffer was drawn.J An article by Miranda found lead soil contamination up to 1 km away from airports where planes use avgas.K
7 Census tract is within 1 km of a railroad. Trains carrying coal are often uncovered, allowing coal dust to travel into the areas surrounding the tracks. Coal has historically and is currently being transported in this manner in California. A layer of railroads in California from Caltrans was used with a 1 km buffer.L A study by Li found lead-contaminated dust up to 1 km away from railroad tracks.M
8 Census tract is within 1,000 feet of a speedway. While leaded fuel for on-road vehicles was banned in the 1990s, the ban did not cover race car fuel, which continued to be used into the 2000s. The United States Environmental Protection Agency noted in their 2006 report on sources of lead that populations living in the vicinity of race tracks were at an increased risk of lead exposure.N A list of speedways in California was extracted from a racing website on April 11, 2019.O A 1,000 foot buffer was used with the assumption that on-road vehicles on highways and race cars on speedways will emit lead particles in a similar manner.
9 Census tract is served by a water district with at least one known leaded service line or fitting. Water service lines and fittings that contain lead pose a risk of drinking water contamination. A list of water service areas with at least one known leaded service line or fitting was extracted from the California Water Board's Lead Service Line Replacement Inventory Status database (last updated August 21, 2019) and was joined to Tracking California's Water Service Area's boundaries extracted on September 25, 2019.P,
A U.S. Census Bureau; American Community Survey, 2015-2019 American Community Survey 5-Year Estimates, Table S0101 Age and Sex; data.census.gov.
B American Academy of Pediatrics Council on Environmental Health. Prevention of Childhood Lead Toxicity. Pediatrics. 2016; 138(1): e20161493.
C American Academy of Pediatrics Council on Environmental Health. Errata, Prevention of Childhood Lead Toxicity. Pediatrics. 2017; 140(2): e20171490.
D Digital Map Products. Digital Map Products Parcel Data – Bulk Data. July 12, 2019.
E United States Environmental Protection Agency. TRI Customized Search: run on September 12, 2019:
F Removal Action Plan (Cleanup Plan): Offsite Properties within the Exide Preliminary Investigation Area. URS Corporation Americas for California Environmental Protection Agency Department of Toxic Substances Control. 2017.
G DTSC Orders Battery Recycler Quemetco to Expand Soil Sampling, Clean Up Areas Near City of Industry Facility (News Release). California Environmental Protection Agency Department of Toxic Substances Control. 2018.
H State Highway Network (SHN) and Postmile System. California Department of Transportation. 2018.
I Strategies to Reduce Air Pollution Exposure Near High-Volume Roadways (Technical Advisory). California Environmental Protection Agency Air Resources Board Research Division. 2017.
J Federal Aviation Administration, Airport Data and Information Portal Advanced Search. 2019.
K Miranda, ML, Anthopolos R, Hastings, D. A Geospatial Analysis of the Effects of Aviation Gasoline on Childhood Blood Lead Levels. Environ Health Perspect. 2011; 119 (10)
L California Rail Network. California Department of Transportation. 2013.
M Spatial Characteristics of Heavy Metals in Street Dust of Coal Railway Transportation Hubs: A Case Study in Yuanping, China. Li, Dongyue and Liao, Yilan. 12, 2018, International Journal of Environmental Research and Public Health, Vol. 15.
N Air Quality Criteria for Lead, Volume I of II. United States Environmental Protection Agency. 2006.
O Racing Tracks Found. RacingIn.com. April 11, 2019.
P Division of Drinking Water California Water Boards, Lead Service Line Replacement Inventory Status August 21, 2019.
Q Tracking California, Water Service Areas. September 25, 2019.