Chemical pollutants released into water or spread through the air are often invisible to the human eye. 释放到水体中或空气传播的化学污染物，通常是不可见的。
However, it is possible that chemical contaminants, pesticides and hormones in the beef could be the reason for these results. 但是，化学污染物，杀虫剂及牛肉种的激素都有可能是导致精子数量减少的原因。
