Nearly every country on Earth has dirtier air than doctors recommend breathing, a report has found. Only seven countries met the World Health Organization’s guidelines for tiny toxic particles known as PM2.5 last year, according to analysis from the Swiss air quality technology company IQAir. Australia, New Zealand and Estonia were among the handful of countries with a yearly average of no more than 5µg of PM2.5 per cubic metre, along with Iceland and some small island states. The most polluted countries were Chad, Bangladesh, Pakistan, the Democratic Republic of the Congo and India. PM2.5 levels in all five countries…