Millions of solar panels in California risk being dumped in landfill sites as they reach the end of their life cycles.
Over the past two decades, more than 1.3m homeowners and builders took advantage of state incentives to install the panels on their rooftops.
However, they have a lifespan of 25-30 years and defunct ones are starting to pile up in dumps, raising fears they will contaminate groundwater with toxic metals such as lead, selenium and cadmium.
California, with abundant all-year sunshine, was a pioneer in the adoption of solar power. In 2006 it introduced the California Solar Initiative, which granted $3.3bn in subsidies for installing panels on rooftops.
While the scheme was considered a success, officials are now grappling with how to safely dispose of the panels.
