Observations (records) with missing values for a variable were dropped from models including that variable. Model coefficients represent the average within-person change in BP for each unit increase in pollution. In nonrandomized studies, confidence limits and p -values do not quantify the confidence or probability that a point estimate would occur within a specified interval due to chance; therefore, we report standard errors of the regression coefficients as a measure of precision and t -values as indicators of the improvement in the fit of the model associated with the exposure variable. Degrees of freedom for t -tests, n -1, are large and can be considered equivalent for comparing t values.
“If you're somewhere in Asia, where your economy has developed by making a lot of goods for developed countries elsewhere, and you're thinking that the health impacts of the pollution are a negative impact on your society, which of course they are, cleaning up is not just a simple matter,” said Steven Davis a researcher at the University of California, Irvine and a co-author on the study. “Because they're obviously concerned about potential impacts on their economy. If they decided to drastically clean up their economy, some other country would step up and say, we're willing to have our people die to have that business.”