Air quality data from the American Lung Association’s (ALA) State of the Air report shows that California is still host to the US’s worst metropolitan areas for air pollution — with potentially lethal implications for residents infected by the coronavirus.

The findings come in the wake of a Harvard University study, which found that “the majority of the pre-existing conditions that increase the risk of death for Covid-19 are the same diseases that are affected by long-term exposure to air pollution”, and that just a small increase in long-term exposure to small particulate matter leads to a large increase in the Covid-19 death rate.

“A small increase in long-term exposure to PM2.5 leads to a large increase in Covid-19 death rate, with the magnitude of increase 20 times that observed for PM2.5 and allcause mortality,” the study said.

The second US state to have recorded a death from Covid-19, California has now lost more than 1,200 residents to the outbreak. Most of the deaths have been in urban centres, many of which have faced severe air pollution for some time.

Among them is the Los Angeles-Long Beach metropolitan area, which tops the ALA ranking for ozone pollution and ranks fourth on year-round particulate matter pollution. More than half of California’s Covid-19 casualties have died in Los Angeles County.

California has long suffered air pollution problems stemming from heavy industry, transportation and environmental events like wildfires — and in many parts of the state, long-term environmental health has for decades been a matter of inequality.

In cities like Oakland and Richmond, which are adjacent to highly polluting industrial sites, people of colour and poor people are to this day more likely to be exposed to toxic air, water and building materials.

On another front, California has for months been fighting an attempt by the Trump administration to revoke the state’s prerogative to set vehicle emissions rules, which the administration says put too high a burden on car companies to bring down their vehicles’ emissions and improve their fuel economy.

After intensive industry lobbying and legal challenges back and forth with several states, California among them, the administration finalised its desired rule change at the end of March, saying it would save the car manufacturing industry $100 billion in compliance costs.