Brazilians 'struggling to breathe' as Amazon burns

Porto Velho, Brazil: Residents of Porto Velho in the Brazilian Amazon have barely seen sunlight in days as a thick cloud of smoke from forest fires en...

Porto Velho, Brazil: Residents of Porto Velho in the Brazilian Amazon have barely seen sunlight in days as a thick cloud of smoke from forest fires envelops their city.

"We are struggling to breathe," said 30-year-old teacher Tayane Moraes, one of some 460,000 people who live in the city near the border with Bolivia.

On Tuesday, the concentration of cancer-causing microparticles known as PM2.5 reached 56.5 micrograms per cubic meter of air in Porto Velho -- 11 times more than the limit recommended by the World Health Organization and the worst of Brazil's big cities.

Inhaling PM2.5 has been found to increase the risk of lung cancer, heart disease, stroke, diabetes and a range of other health problems.

On August 14, the level was a "dangerous" 246.4 micrograms per cubic meter, according to the IQAir monitoring company.