Between 17, 500 and 25, 400 feet in elevation, the snow and soil samples they tested exceeded the U.S. Environmental Protection Agency's tolerance levels for both arsenic and cadmium.
The upper and lower extremes of environmental conditions which members of a species can survive are the species limits of tolerance.
种的成员能够生存的环境条件上限和下限是种的耐受限度。
3
Environmental toxins or genetic susceptibility may account for some cases. Drug therapy requires careful scheduling and combinations to delay development of tolerance and side effects.