Air quality controllers warned on Friday that several Swedish cities have experienced high levels of airborne particles (particular matter or PM). The dry weather has meant that all the grime churned up by winter tyres is no longer stuck to the surface of the road, instead swirling into the air.
"Whatever the studded tyres tears up is collected during the winter, and as long as the roads are wet it stays put," said Lars Burman at Stockholm and Uppsala Counties Air Quality Association (Stockholms och Uppsala läns luftvårdsförbund - SLB), an NGO that keeps track on inner city pollution.
"Then when it dries up, it starts swirling about," he told the TT news agency.
SLB noted in its annual report that Stockholm did not live up to its air quality goals last year. Similar measurements from cities across Sweden were similar.
The NGO has tickers on its site and stated that on Friday, one in three vehicles going through central Stockholm was fitted with studded winter tyres. In Uppsala, more than two of three cars were rolling with winter tyres on.
Both the particle pollution and carbon-dioxide were up, with Friday's staple soaring in angry "high level" red on the graph.
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The sunny dry weather in conjunction with pollen were deemed responsible for a double blow on Swedish allergy sufferers.
The PollenRapport.se website noted on Friday that willow and pussy willow were blossoming all the way up above central Sweden and in a stretch along the east coast. Northerners faced alder tree pollen. Hazel trees were already in bloom in March.