Chemtrails: for weather change

Chemtrails of Maui, is this true? My friend Patricia, whom I've know for two years works at Basil Tomatoes as a waitress. She Introduced me to this chemtrails. As she says, one time when she looked up into the clouds and see the planes and a minutes passed by, there some strange white smoke from the plane in the clouds. Maui chemtrails could be fatal to our health.
     I tried to search in the net to check what was this all about. This is the aerosol spraying from white planes diffusing chemicals into a cloud formations.(http://site.ebrary.com/mcc/Doc?id-10297182&ppg=112)
     And this aerosol contains ethylene dibromide, aluminum oxide, barium salts, strontium, cadnium, mercury,decussated red blood cells, live biological toxins radio active thorium, yellow fungal mycotoxins and mold spores mycoplasma.(http://stopsprayingcalifornia.com/Hawaii_Chemtrail_Reports.php)
     Who and why do people spray such that chemical? What are their purpose?