[TL;DR Literally everyone is contaminated with a lot of pollutants]
Many man-made chemicals & materials we use, or used, in agricultural, commercial, and industrial purposes have/had devastating consequences. The full extent of the long term consequences on the human body and global ecosystems are barely understood. It is extremely evident we often discover things are dangerous only well after its widespread use.
“You will observe with concern how long a useful truth may be known, and exist, before it is generally received and practice on.” - Benjamin Franklin
Piston-engine aircraft still use leaded fuel (avgas)
Persistent Organic Pollutants (POPs)
POPs are toxic carbon-based chemicals that do not break down for thousands of years. They are often the direct products or by-products of industrial processes and chemical manufacturing.
DuPont was historically the world’s largest chemical company by sales before its merger with Dow chemical company in 2015. It has an infamous history of unethical corporate practices. While they brought us great inventions such as neoprene, nylon, mylar, lycra, and kevlar; they also brought us teflon, Freon, and a variety of other toxins that pollute the world to this day even after being banned.
Plastic Associated Chemicals (PACs)
Similarly to POPs, PACs can take forever to break down and heavily disrupt all the vital functions of our bodies. No natural microbes can process these materials with their unnatural polymer bonds so UV light is the only source of decomposition. There is some research in this area to engineer plastic eating microbes, but the area is very embryonic.
The variety of man-made toxins present in our environment is honestly mind-blowing. At this point it is entirely impossible to avoid exposure to all of these compounds.
Population Trends
These pollutants are just the tip of the iceberg. We seem to be seeing a concerning trend of populations having less children as they become more developed. As more countries become developed we may see an all time high and continual decline in global population. If we look at the statistics we see a huge decline in fertility rates (children per woman) already. Keep in mind the replacement rate is 2.1 children per woman to maintain population.