One of the strongest areas of research today links polluted air, especially PM2.5, to declining sperm health. A major study published in JAMA Network Open (2022) found that exposure to particulate matter was associated with lower sperm count, motility and higher sperm DNA fragmentation. The study was conducted on men in China, and it found how for 33 876 Chinese men, decreased total and progressive sperm motility and increased risk of asthenozoospermia were associated with exposure to particulate matter of less than 2.5 μm and 10.0 μm or less.