Polycyclic aromatic compounds (PAHs) are created during burning of everything from oil to wood to cigarettes, and many are carcinogenic.

The regional district says the ozone could persist until Monday or longer if hot weather sticks around.

"It's another plague, unfortunately. It's another plastic plague that we're facing now," said Dr. Hilary Nash

Researchers say that the new levels of microplastic pollution now ranges from 12-125 trillion, up from the previous estimate of 5-50 trillion.

The slowing economy due to COVID-19 has allowed solar, wind and hydro power to overtake coal-fired power.

According to researchers, the improved enzyme breaks down 90 per cent of plastic bottles for recycling within a span of 10 hours.

Photos show the dramatic difference in L.A.'s skyline since California's stay-at-home policy came into effect due to the novel coronavirus.

'For something that happened so suddenly to change emission patterns so much, is very much unprecedented,' says an environmental analyst.

Air pollution, particularly CO2 emissions, have declined around the world, including parts of Asia that are 10 to 30 per cent lower than normal.

Satellite imagery shows the high levels of nitrogen dioxide over China went down as lockdowns and factory closures were enforced earlier this year, but it's starting to rise again as cases drop.