Human Sperm in Dramatic Decline Scientists Warn Posted
By Aaron Derfel, Montreal Gazette, 7-3-1

Scientists from around the world are alarmed by a dramatic increase in genetically damaged human sperm - a trend that is not only causing infertility in men, but also childhood cancers in the offspring of those who can reproduce.

It's now estimated that up to 85 per cent of the sperm produced by a healthy male is DNA-damaged, a leading authority on the subject revealed yesterday at an international conference being held in Montreal.

"That's very unusual," said John Aitken, head of biological sciences at the University of Newcastle in Australia.

"If you were to take a rat or a mouse or a rabbit, usually more than 80 per cent of their sperm would be normal."

For the last 20 years, scientists have known about declining sperm counts. But researchers are now learning that the quality of human sperm is steadily eroding, and might be causing birth defects as well as brain cancer and leukemia in children.

Abnormal sperm is also being blamed for a global increase in testicular cancer - a disease that strikes men in their 30s. Scientists believe that when a DNA-damaged sperm fertilizes a woman's egg, it can trigger a mutation of a key gene in the embryo.

And even if men today can reproduce, their damaged sperm might lead to infertility in their male progeny, Aitken suggested. "You're likely to see lots of diseases that are related to poorer semen quality."

Scientists suspect a wide range of environmental causes for the abnormal sperm - from exposure to pesticides and heavy metals to electromagnetic radiation.

"We're all exposed to 10 times more electromagnetic radiation than our forefathers," Aitken said. "It's all the electrical appliances we use, including microwave phones."

There is a consensus in the scientific community that men who smoke cause damage to their sperm, and that this might be responsible for childhood cancers. "If you are a man and you smoke, your semen profile won't be obviously affected," Aitken said. "You'll still have lots of sperm swimming around and you'll be fertile. But the DNA in your sperm nucleus will be fragmented."

The average ejaculate of human sperm contains 80 million spermatazoa, each genetically programmed to fertilize a woman's egg. Scientists examining human sperm have discovered that not only are sperm counts on the decline, but that the vast majority of sperm is sluggish, poorly structured, their DNA fragmented and that they generate a lot of cellular waste called free radicals.

"Generally speaking, everything is bad with the sperm," Aitken said.

Fortunately for most couples, it's the undamaged or least damaged sperm that tends to fertilize the egg.

As a result of increasing male infertility, scientists have developed a new technique to help couples conceive. It's called Intra-Cytoplasmic Sperm Injection (ICSI). In the lab, a technologist will take from the would-be father a single sperm, or even a cell that is on its way to becoming a sperm, and fertilize it in the test tube with the woman's egg. The resulting embryo is then transferred to the woman's uterus.

Dr. Keith Jarvi, of the University of Toronto-Mount Sinai Hospital, said the ICSI technique has revolutionized the treatment of male infertility. But he wondered about the health outcomes of the ICSI children.

That human sperm is of poorer quality than that of other mammals is not surprising. The human species is the only one that wears clothes, and healthy sperm need to be kept a couple of degrees cooler than the full body temperature. But clothing alone is not responsible for the extent of abnormal human sperm, Aitken argued.

Aaron Derfel's E-mail address is {} (c) 2001, The Montreal Gazette,