[wiki]

Is there anything other than cocaine that can show trace amts. of benzoylecgonine in a urine test from  a race dog? Are there any environmental factors that can factor?

[Arkcon]

Is there anything other than cocaine that can show trace amts. of benzoylecgonine in a urine test from  a race dog? Are there any environmental factors that can factor?

Possible there are other factors, but they're usually accounted for in the assay's design.  It really all depends.  As a general rule, if the report has the text: "confirmed by GC/MS", then no, the lab is using a very rigorous assay.