Not a suprise really.
Similar type studies have made the news:
They have tested the waste-water-ways in Italy for the cocaine metabolite and have found HIGH concentrations of it.
THere was another done where they tested surfaces in the house of lords in England and found HUGE amounts of trace cocaine of 90% of the surfaces.
95% of all money has trace amounts of cocaine on it.
I lick every dollar bill that goes through my hands now.