Wildfires pollution is serious than industrial pollution?

A report from USA today stated that U.S. and European "megacities" look less smoggy over the past decade, while ones in China, India, the Middle East and Africa look worse. Meanwhile,it quotes a research from Scientific Research Publishing(SRP or SCIRP) which make use of aerosol pollution data analysis come to this conclusion. The report said it’s air pollution led by wildfires rather than  industrial that dogs these smoggy cities.

I have a question.Why wildfires pollution is serious than industrial pollution?In this cities, how much they burn each year?