Table 3.

Postnatal environmental factors associated with risk of childhood asthma.

Increased risk of childhood asthma	Decreased risk of childhood asthma
Environmental tobacco smoke exposure [60, 81–84]	Exposure to a farming environment [68]
Exposure to traffic exhaust and air pollution [64, 85, 86]	Breastfeeding [87, 88]
Rhinovirus-related wheezing [89]
Early exposure to acetaminophen [90]
Broad spectrum antibiotics used in early childhood [91]
Early introduction of solid diet at infancy [67, 92]