4)69; there was no association between mouse allergen exposure in infancy and later wheeze. A third small cohort reported no association between exposure to cockroach allergen in infancy and wheeze in the first 2 years of life.52 Observational studies report associations between exposure to feather quilt in infancy and reduced asthma at 4 years compared with selleck chem Nilotinib non-feather quilt (OR 0.4)70 and that a greater number of synthetic items of bedding (known to be HDM rich) during infancy was associated with increased risk

for a history of asthma by 7 years (OR 1.8).71 HDM exposure: There were two intervention studies72 73 and one observational study,74 and none found an association between exposure in infancy72 73 or by 2 years of age74 and asthma at 3,73 6–774 or 8 years of age.72 Outdoor allergens: Three cohort studies were identified and all found exposure was related to increased asthma risk. One study related fungal spores and pollen concentrations at the time of birth to wheeze at age 2 years and those born

in autumn to winter (the fungal spore season) were at increased risk for wheezing (OR 3.1).75 A second study reported an association between increased grass pollen exposure between 4 and 6 months of age and increased asthma at 7 years of age (OR 1.4).76 The third study related tree canopy cover (a source of tree pollen and also of altered airflow and air quality) in infancy to asthma at 7 years and found a positive association (RR 1.2).77 Air pollution One meta-analysis and eight additional cohort studies were identified, and while pollutants associated with combustion were associated with increased asthma risk, no single pollutant was consistently identified. The meta-analysis found that exposure to Nitrogen Dioxide (NO2, OR 1.05), Nitric Oxide (OR 1.02) and Carbon Monoxide (CO, OR 1.06) were associated with higher prevalence of diagnosis of childhood asthma. Exposures to SO2 (OR 1.04) and particulates (OR 1.05) were associated with a higher prevalence of wheeze in children.78 Ambient lifetime CO exposure, but not NO2, ozone or particulates with mass

less than 2.5 microns (PM2.5), was associated with increased risk for wheeze AV-951 at 5 years (OR 1.04 per ppm increased CO).79 A second cohort study found that ambient exposure to NO2, but not ozone, SO2, PM2.5 and PM10, was associated with increased asthma risk at 3 years (OR 1.2 per 5ppb increase).80 A third study related averaged lifetime exposure to ozone, CO, NO2, SO2 and PM10, and found no association with asthma in 7-year-olds for the whole population, but among the 10% with previous bronchiolitis, asthma risk was increased (OR approximately 7) in association with higher exposures to ozone, CO and NO2 (table 2).81 Exposure to traffic-related particles (elemental carbon attributable to traffic) during infancy was associated with increased risk for asthma in 3-year -olds (OR 2.