A finding noted that high exposure to spores and pollen in the first 3 months of life in newborn increases the risk of early childhood wheezing. In the Salinas Valley the researchers measured ambient aeroallergen concentrations from October 1999 through July 2003, and defined distinct seasons of high spore and pollen concentrations. This interval encompassed the in utero period and first 24 months of life of the 514 children in the study. Moreover the authors reviewed medical records for reports of early wheezing in all the children and measured peripheral blood levels of Th1 and Th2 type cells at age 2 to determine whether cytokine profiles are related to early exposure to aeroallergens. A clear seasonal pattern was observed, according to the authors. Relative to children born outside the spore and pollen season, the unadjusted odds ratio (OR) for early wheezing for those born during the spore season was 2.8. This association persisted after controlling for confounders. Increasing mean daily concentrations of basidiospores and ascospores, as well as increasing mean daily concentrations of total and specific pollen types, in the first 3 months of life were also linked with higher odds of wheezing. Dr. Harley's team noted that the ambient spore concentration in the first 3 months of life was positively associated with Th1 levels and Th1:Th2 ratio and the early-life pollen concentration was negatively associated with Th1 levels at age 2 years.