There was no evidence of a threshold. Sulfur dioxide levels were not significantly associated with increases in the death rate. No epidemiological study can prove a cause and effect relationship because it is always possible that some key factor was not considered. Until last month, skeptics could say smoking might explain why death rates increase as PM10 concentrations increase. Smoking has now been ruled out.
All scientific work is liable to be upset or modified by advancing knowledge.
That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time. For the 8th, see footnote 5. 20 and 23 for discussion of the Steubenville study. We would like to continue to provide this service free. Please do not send credit card information via E-mail.