Some 19 locations — including pre-schools, parks and day-care centres — in a 1.7 mile radius around the 15-acre Exide Technologies battery recycling plant in Vernon, California are being tested for lead contamination.

The work is contained in the Supplemental Sampling Workplan for Schools and Parks in the Vicinity of the Exide Facility released mid- November.

Working under the California Department of Toxic Substances Control, regulators at EFI (Engineering, Fire and Environmental Services) are still canvassing neighbourhoods to identify any other properties that should be targeted, so the number of locations could increase.

Soil in the areas of Maywood, Boyle Heights, Huntington Park, East Los Angeles and Bell is being sampled under the plan, which is scheduled for completion by the end of the year.

So far at least 4,400 residential properties have been sampled, which is just under half of the targeted number. Up to 250 have been cleaned up.

In August 2015, the CDTSC said testing had shown that at least 10,000 homes had been contaminated with toxic dust.

That October, the Los Angeles County Board of Supervisors allocated $2 million to hire specialists to carry out soil testing, and in February 2016 the state allocated almost $180 million to fund the testing and clean-up work.

A smelter had been in operation at the Vernon plant since 1922. In 1981, owners Gould Inc were given a permit to operate as a battery recycling plant under ‘interim status’. The Exide Corporation took over the plant in May 2000, as part of its acquisition of GNB Technologies.

Two years later Exide filed for Chapter 11 bankruptcy protection, and in 2008 the firm was ordered to cut production by half after complaints were received about ash fallout.

However, it wasn’t until April 2013 that regulators ordered operations to be suspended, and in March 2015 Exide Technologies was ordered to shut down, demolish and clean up its site after striking a deal with federal officials that meant the company would not face criminal charges.