Enviromental and Agriculture question?

there is a 25 acre mountain lake...this lake is surrounded by 300 acres that was a commercial apple orchard from 1950-1996...the trees were pushed up in 2000 and now the land is pasture..my question is this....is the 25 acre lake safe for fishing and swimming since all those years there was drainage of sprays and Poison from the apple orchard? or would this lake not be safe at all? i do not know if after time the Poison that was applied just goes away and all is ok... thanks