Figure 1. Daily number of visits, weight of the sediment, and minimum
temperature in Araraquara during the period of study.
Minimum Temperature (°C) Sediment Weight (mg) Number of Visits
Date
There is a significant correlation between the number of
visits and sediment weight (0.36, p < 0.01). Interestingly,
there is a lack of correlation between sediment weight
and temperature (0.10, p > 0.05). In fact, the association
between inhalation counts and sediment weight was not
sensitive to temperature in all models explored in this
study. Table 2 shows the estimates (coefficients and 95%
confidence intervals) for the Poisson regression model
adjusted. We found a significant relation between the
number of visits and the amount of sediment (2-day moving
average). The relative risk associated with an increase
of 10 mg in the sediment weight was 1.09 (1.00–1.19). A
clear threshold effect was observed when categories of
sediment weight were used instead of continuous data, as
depicted in Figure 3. Only the fourth quartile of sediment
(above 17 mg) presented significant association with inhalation
therapy, exhibiting a relative risk of 1.20 (1.03–
1.39). No evidence of significant autocorrelation was
detected in the models.