Should be worldwide. There are some studies that point towards microplastics being the main cause. Its certainly a very difficult thing to study
In any case, I am not as concerned as others. As long as you try, you will eventually "score". IMO the most serious problem in demographics is that people are actively taking measures to avoid conceiving a child.
Anyway, its not only microplastics, it is also about obesity, smoking, taking drugs (marijuana), chemicals in various everyday products such as plastic bottles, metal food cans, detergents, flame retardants, food, toys, cosmetics and pesticides. Its a mess, just think about how much exposure we have with these things everyday..