But while most people know that mold thrives in poorly ventilated and moist environments and indoor smoking worsens the air quality, fewer consumers know that toxic chemicals also lurk in everyday products purchased at the grocery store.

FORBES: Hidden Household Toxins

Not smoking, eating a high-quality and healthful diet, not being overweight and being physically active all contribute to a person's health, he said.

CNN: Thin is in, but fat might be better

As long as those who have bad habits are not compromising the quality of health care being provided on hospital ground, then let's not exclude smoking nurses, fat physical therapists, and scuba diving pharmacists from work.

CNN: Barring smokers from hospital jobs unfair

While the study took into account factors that can affect sperm quality, such as age, researchers were unable to control for socio-economic factors, smoking or weight, which have been shown to have a major impact.

BBC: French sperm count 'falls by a third'