May 7 is World Asthma Day. I was 6 when I had my first asthma attack. The initial trigger wasn’t clear but there were the usual suspects; house mites, cat allergens, family stress, London air quality. This wasn’t the pea soup smog of the 1950s, but rather the late sixties when private car use sky-rocketed and transport emissions replaced smoke from household fires as a primary pollutant.