It has long been known that pregnant women should avoid fish caught in the Baltic Sea and in freshwater lakes but new research indicates that the genetic make up of 20 percent of men also puts them in the risk zone.
Researchers at Malmo, Lund and Åhus University hospitals have found that toxic substances such as PCB and dioxin affect sperm production.
The studies involved 680 men from Sweden, Poland, Ukraine and Greenland. Among those that had the genetic variation and had been subjected to high levels of toxic substances found in the fish, sperm counts were 40 percent lower.
The researcher leading the study, Yvonne Lundberg Giwercman, argues that recommendations to avoid the consumption of the Baltic and freshwater fish should be extended to men seeking to become dads. But the National Food Administration (Livsmedelsverket) has no plans to change its recommendations.
"The research is very important but before we change the food recommendations for Baltic Sea fish we would like to see similar results from other research groups," said Anders Glynn at the administration to Sydsvenskan.
The toxins PCB and dioxin are commonly occurring in Swedish nature but have been in decline in recent decades. In the Baltic Sea levels have however remained constant since the early 1990s and levels of mercury are increasing.
The poisons are stored in humans and animals and stay in the body for a long period of time.