Acids are from car exhaust, the nitric and nitrous acid is from diesel combustion in most cases, the sulphur is from both diesel and petrol combustion, as both contain sulphur in them. Carbonic acid from CO2 in the air. Particulates are rubber worn off tyres, lead as residual lead in unleaded fuel ( which does contain a little lead, as it was either made, stored or pumped through old piping which had leaded fuel in it, plus a minor amount from lead based solders in piping and metal piping). Carbon is from incomplete combustion, which makes that brew of carbon black containing this. Skin because most dust indoors is made up from skin particles, outdoors a part is from skin, but also paint particles, pollen, fibres from vegetation and such.