Marcela Herrera wiped sweat from her nose as the screeching sound of a saw cutting lumber mixed with mariachi music blaring from a house across the street. Clipboard in hand, Herrera jotted down addresses in this Pacoima neighborhood where lumber, steel, ironworks and heavy equipment rental shops operate near homes.
A few blocks away she noted a child care center, where youngsters played outside in air that reeked of a chemical.
"There are a lot of hazardous waste sites around my house," Herrera said in Spanish through an interpreter. "I wanted to do something to help out."
Frustrated because she must keep her asthma- and bronchitis-suffering daughters indoors to protect their health, Herrera recently joined a cadre of northeastern San Fernando Valley residents to catalog the location of industrial businesses and their proximity to gathering places for young and elderly residents, who could be most affected by contaminated air and water.
The effort, known as "ground truthing," is part of an ambitious project devised by environmental justice researchers and a local nonprofit group to compile an accurate picture of where toxic and hazardous sites are located in Southern California and how they affect the health of nearby communities.
"The idea is to try to find the truth on the ground, and we thought, 'Who better than the residents?' " said Michele Prichard, director of change initiatives at the Liberty Hill Foundation. The organization paid residents this summer, in communities including Pacoima, Van Nuys, South L.A., the Figueroa corridor downtown, Boyle Heights, Maywood, Commerce and Wilmington, to walk select neighborhoods and write down what they saw.
Updated information is necessary because state and federal environmental databases that track industrial uses by location or type of pollution they emit are incomplete, said James Sadd, a professor of environmental science at Occidental College.
Without data that show the full picture, lawmakers have a hard time drafting laws to protect neighborhoods and can't accurately target cleanup efforts, residents and researchers said.
"It is a challenge to look at cumulative risk," said Alvaro Alvarado, an air pollution specialist with the California Air Resources Board, which funded similar research by Sadd and others in Oakland.
State officials said they will use the Oakland data -- which showed significantly more hazards near places where children or the elderly congregate than were recorded in state databases -- to determine whether they should rework their database, Alvarado said.
In Los Angeles, preliminary results from the surveys show that state databases also significantly understate the number of automotive businesses in Wilmington and Boyle Heights.
Sadd, working with Manuel Pastor, a professor of geography at USC, and Rachel Morello-Frosch, a professor of community health at UC Berkeley, uses a computerized system that combines census and socioeconomic data with state and federal information that documents where industrial sites are located. The system generates color-coded maps showing that pollution hot spots are typically concentrated in minority neighborhoods throughout the Southland.
State regulators said they are also interested in comparing the Southern California research to their databases. Los Angeles officials hope to use the results to identify hot spots where industrial sites abut homes. The data can be used to help community planners work out neighborhood zoning issues, such as what type of businesses can open or whether housing should be allowed on a particular street.
"Some communities suffer more pollution because city officials have historically relied on poorly written community plans that allowed incompatible use," such as an industrial shop that uses toxic substances operating near homes, said Regina Freer, a Los Angeles planning commissioner.
"There are some places where there are some horrible incompatible uses that won't be rectified, even with new community plans," said Freer, adding that the planning department hopes to use the data in policy decisions.
Residents say the Los Angeles effort comes at a crucial time for many communities, as large lots adjacent to industrial centers are awaiting redevelopment.
On a recent walk in Boyle Heights, a block bounded by South Evergreen Avenue on the west, 11th Street on the south, Dacotah Street on the east and Olympic Boulevard to the north, members of Union de Vecinos, a local grass-roots tenant advocacy group, wrote down what they saw:
An alley used by diesel-powered freight trucks hauling goods to and from Vernon.
A warehouse where a husband and wife pieced together cloth for nearby garment factories.
A storefront where workers in knee-high rubber boots wheeled a container of raw poultry onto a truck.
An auto parts center that's 300 feet from the neighborhood's only public park.