Which of the following can directly affect male fertility?

Environmental toxins can have a significant impact on male fertility due to their interference with hormonal balance and sperm production. Exposure to certain chemicals, heavy metals, and other pollutants can lead to decreased sperm count, poor sperm motility, and even genetic damage to sperm. Such toxins can disrupt endocrine function, which is critical for maintaining normal reproductive health.

In contrast, while excessive exercise, dietary habits, and stress levels can also influence fertility, they often do so through indirect mechanisms or do not have as pronounced an effect as environmental toxins. For instance, excessive exercise can lead to hormonal imbalances, and poor dietary habits may affect overall health, but environmental toxins pose a more direct and immediate threat to male reproductive capabilities. Understanding these factors is vital for addressing and mitigating risks associated with male fertility.