In California around the time of the study -- 2004 and 2005 -- hundreds of people were sickened by West Nile virus and 48 died. Most people exposed to the disease do not have symptoms, but in about 1-in-150 people it can be fatal or result in permanent neurological effects.
The study evaluated emergency room visits in Sacramento County hospitals on days that pesticides were sprayed as well as the three days following spraying. Spraying was done in north Sacramento over three nights, and in south Sacramento over four nights in August 2005. Data were compared with emergency room visits on other days during the same period as well as from nearby areas that were not exposed to aerial spraying.
Emergency room visits were classified by specific diagnostic categories, including respiratory, gastrointestinal, skin, eye and neurologic diseases. Importantly, they found that exposure to aerial spraying was not associated with increased rates of emergency department visits for any of these conditions.
More than 250,000 emergency room visits were analyzed and stratified by 785 diagnostic codes. According to Geraghty, because there were so many data points, statisticians predicted that by chance alone, two conditions would appear to have occurred too frequently or too infrequently. In fact, a type of abdominal hernia was found to occur more often than the background rate during the time of spraying, and death and disease due to unusual causes was found to occur less frequently. The authors concluded that because these conditions have no known plausible b
|Contact: Charles Casey|
University of California - Davis Health System