To understand the burden of lead poisoning in California, it is important to identify who has evidence of lead exposure in their blood. Blood lead levels are measured when a child’s blood is drawn in a hospital, clinical, or public health setting and tested for the presence of lead. Screening for lead means doing a blood lead test.
Data Sources
Childhood Blood Lead Level (BLL) Data
Since 1986, the Childhood Lead Poisoning Prevention Branch within the California Department of Public Health has been legislatively mandated to collect information on childhood blood lead levels, identify lead burdened children and see that they receive appropriate services, and prevent environmental exposures to lead. This includes maintaining a statewide database, the Response and Surveillance System for Childhood Lead Exposures (RASSCLE II) with blood lead levels and other demographic information about children who have been screened (blood lead tested). The database is used by the state Childhood Lead Poisoning Prevention (CLPP) Branch to work with local CLPP Programs to conduct surveillance activities, case management, and other necessary follow-up with children who have blood lead levels of concern.
Housing and Poverty Data
Data on the age of housing and children living in poverty are from the 2000 U.S. Census, Summary File 3. Housing and other demographic information about the U.S. population are collected by the U.S. government via the U.S. census every 10 years.
The data can be downloaded directly from the U.S. census website: www.census.gov.
Statistical Concepts
Counts
The number of California children with a certain blood lead level is calculated by summing the total number of tested children in a specific age group (e.g. 0-5 years old), for each blood lead level (i.e. 0-<4.5, 4.5-<9.5, 9.5+ μg/dL), for each year, and by county. The blood lead levels reported on this website are unique per child. That is, these data include only the highest blood level reported per child if they were tested more than once.
Percentages
The percentage of California children with a certain blood lead level is calculated by dividing the counts by the total number of children tested for each age group, for each year, and by county.
Limitations
Childhood Blood Lead Level (BLL) Data
Laboratories began reporting all blood lead level data electronically to the Childhood Lead Poisoning Prevention Branch (CLPPB) in 2005. Prior to 2005, only elevated levels were reported and not all data were electronic. Due to these changes in data reporting, 2007 is the first year of the most complete data.
Housing and Poverty Data
The U.S. census group housing data by 10 year increments (1930-1939, 1940-1949, etc). Although lead-based paint is a concern for housing pre-1978, the data on the age of housing are reported through 1979. The U.S. census do not include information on renovations or on the condition of the housing, which may affect the risk of lead exposure.
Number of children less than five living in poverty does not capture all children who may be living in substandard conditions.