The newspaper Aamulehti reported about the preliminary findings of the study in its Sunday edition. They suggest that under-20-year-old men in Finland produce 30 to 45 percent less spermatozoa than 30-year-old men.
Whether the sperm count among young Finns has really fallen will not be known with certainty for another three years when the study should be complete.
Male fertility in Finland has been among the highest in the world.
The findings of a fall in male fertility reflect the results of similar studies in other countries.
Concern over a fall in sperm counts emerged after a study in Denmark noted a significant fall in male fertility. Since then, similar discoveries have been made in studies in, for example, France, Greece and the U.S.
A researcher at Turku University said that the big question is what has taken such a great toll on young men's sperm count.
Scientists have ascertained that smoking during pregnancy has an adverse effect on an unborn male child's future fertility.
Another reason could be toxic chemicals in the environment. Very little is known about how the majority of chemicals used in the European Union affect fertility and the sperm count.