“If mercury was the cause, then how did so many of my (older) generation get these shots without any problems? Why is autism on the rise as thimerosal use decreasing?”
One possibility - your (my?) generation received far fewer vaccinations, generally at an older age.
“What about in the days when mercury was used indiscriminately in industry? Many people were exposed to mercury and had symptoms and some died from it, but where is the documentation of autistic like symptoms in children widespread throughout the population in those days?”
Different forms of mercury have different modes of toxicity. Pure (elemental) mercury is relatively safe compared to the organic forms (e.g. methylmercury). The mode of entry is also a factor, people used to drink mercury with few side effects unless the exposure was frequent and long term. On the other hand, inhaling mercury vapor has much quicker effects (mad hatter’s disease). Finally, direct injection of small amounts of organic mercury compounds can be deadly, even in small amounts. Also, as noted earlier, each person has a different ability to metabolize (and ultimately excrete) mercury. Some people who are lucky enough to quickly rid themselves of mercury have few or no problems, while others who retain mercury quickly develop symptoms.
Makes sense.