I can see this being the next foundation for all things evil about chemtrails -
SEE - THEY ARE POISONING US!!
Obviously "many years exposure" is not the same as being 35,00 feet under flight paths or even near an airport - as a health and safety issue it is more likely to be something that mechanics and refuelrs and fuel company staff have to worry about.
My father was an aircraft mechanic at the Alameda Naval Air Station in CA for over 20 years. He worked on the jet fuel systems and that required crawling around in the wings. When he came home from work he always smelled of jet fuel and his jeans and wallet were saturated (wet) with jet fuel. He also used solvents to wash parts.
Amazingly, his health was really good and he lived to age 86. However, when he was in his mid 50's he got bladder cancer. I always wondered if the jet fuel caused it, but his doctors said the bladder cancer was from smoking. He grew up on a farm and he started smoking home rolled tobacco at a young age. Then he smoked Camel cigarettes (without filters) until Nat King Cole died in 1965. When it was announced that smoking causes lung cancer and that's what killed Nat King Cole, he quit smoking. By that time he had smoked for about 30 years, so it very well could have been the smoking (and not the jet fuel) that caused his cancer. He had chemotherapy for the bladder cancer and it never did return.
That being said, everyone is different and chemicals can affect people differently. I have Multiple Chemical Sensitivities and I probably couldn't stand being exposed to jet fuel for any length of time. I have an MTHFR enzyme deficiency (gene defect) which reduces my ability to detox by about 40%. But people who inherited defective genes from both parents can have a 90% reduction in their ability to detox. So I would imagine that any health effects from jet fuel would depend on the length of time one is exposed, the quantity/concentration they are exposed to, the route of exposure (skin, lungs), and how well the person's detoxification (methylation) cycle is working.