Men's sperm quality is falling every year, according to a study, with experts fearing that modern life is destroying male fertility.
Fertility clinics found that the number of moving sperm – or ‘swimmers’ – in men’s samples has dropped by 1.8 per cent each year.
Meanwhile, another study found that male fertility is declining in five out of six US cities.
Its authors say the findings could be a ‘public health warning’ and that junk food, lack of exercise and pollution may be fuelling the crisis.
Only last year experts warned that the human species could face extinction, after it emerged that the average sperm count in Western countries had more than halved in a generation.
The new findings are to be presented this week at the annual meeting of the American Society for Reproductive Medicine in Denver, Colorado.
Researchers led by the Sidney Kimmel Medical College in Philadelphia and fertility clinic IVIRMA monitored almost 120,000 men seeking treatment for fertility problems in Spain and the US from 2002 to 2017.
The men were put into three groups based on the millions of swimming sperm in their semen samples.
Measuring ‘swimmers’ is seen as a better way of judging fertility than sperm count alone.
Among American men in the most fertile group, who had more than 15million moving sperm, this went down by 1.8 per cent for each year of the study.
Between 2002 and 2005, 84.7 per cent of men were in the most fertile group, but this fell to 79.1 per cent between 2014 and 2017.
At the same time, the proportion of the least fertile men rose. Those with poor fertility, from five million swimming sperm to none, increased from less than 9 per cent of the total to 11.6 per cent.
Dr James Hotaling, a co-author of the study, said: ‘We did not expect to see the same fall in sperm quality in Spain and the US. If this trend continues, there is potential for more men to become infertile.’
Commenting on the study, a UK expert, Professor Charles Kingsland, of CARE fertility, said: ‘Our change to a more sedentary lifestyle has no doubt had an effect, as has our diet because men tend to eat far more rubbish than they did a generation ago.’
The second study, led by Icahn School of Medicine at Mount Sinai, New York, involved more than 2,500 sperm donors.
It found that fertility declined over 11 years in Los Angeles, Palo Alto, Boston, Houston and Indianapolis. New York was the only one of the six cities studied to buck the trend.
Sedentary lifestyles are believed to lower sperm production, while cheap and saturated fats found in junk food are known to harm sperm counts.
The chemical bisphenol A (BPA), widely used in plastic wrappers and containers, has been found to be toxic to sperm.