Helsinki City Transport buses, trams, and underground trains carry 687,000 passengers on a weekday. Of the passengers, 0.13% travel with a pet. We interviewed passengers and measured allergen levels in vehicles to determine what difficulties allergens cause to passengers with allergy and asthma.
Of 2,021 interviewed passengers, 14% complained about inconvenience caused by pets, usually health problems. Of 324 adult passengers with allergy or asthma, 53% had experienced symptoms in public transport; the corresponding figure for 75 children was 32%. The median concentration of the main dog allergen, Can f 1, in dust from seats and floors in public transport vehicles was 2,400 ng per g of dust (range 20-8,500 ng/g). For the main cat allergen, Fel d 1, the median was 870 ng/g (range 3-2,600 ng/g). These levels can be regarded as low or moderate, and they cause symptoms in sensitive persons. Concentrations of mite allergens were undetectable or low. Allergen levels were lower in vehicles where pets were not allowed than in vehicles where pets were allowed, lower in dust from uncovered seats than in dust from seats with a covering, and lower after cleaning vehicle floors and seats than before cleaning.
Dog and cat allergens are present in public transport vehicles in Helsinki at levels that cause symptoms in sensitive persons. Prohibiting pets would probably bring only a modest reduction in levels, as few pets are carried, and much allergen contamination comes from passengers' clothes.