Some people attribute infertility to a problem with the woman. However, 35 percent of infertility cases are due to problems with male factors. Male infertility is becoming more common. Research suggests the cause of declining male fertility can be environmental factors such as pesticide and chemical exposure, medication, drug and alcohol use, pollution, and radiation. Sometimes men are exposed to toxic substances at work, leading to infertility. Or, they might expose the scrotum too often to high temperatures, killing the sperm. Environmental factors are just one cause of infertility.