Almost all the thimerosal exposure that was mandated under the US vaccine schedule in place before 2001 occurred during the first 6 months of life as a result of vaccination with DPT, Hepatitis B, and Hib B. This fact takes on particular interest when combined with the fact that ethyl mercury, which is the culprit under the thimerosal causes autism theory, only stays in the human body for a relatively short period of time which keeps it from accumulating – it has a half life of about 4-7 days. A third fact is also important: heavy metal toxicity generally results from the accumulation of heavy metals to high enough levels to cause damage – everyone has nearly every common heavy metal in their system at the same time at some level, from aluminum to chromium to mercury; in fact, many heavy metal are crucial to life at low doses. The key to whether damage results is concentration.

These three facts would logically demand that if thimerosal were to cause autism, it should induce autistic symptoms in the first 6 months of life, or within a month or two thereafter, because ethyl mercury exposure through thimerosal containing vaccines drops precipitously thereafter (or at least did when thimerosal was still in the DPT, Hep B, and Hib B vaccines). To the contrary, autism shows up at many different times during the first couple years of life. Some kids come out of the womb with obvious signs of autism, such as the inability to accept the touch of their mother and eye contact aversion. Other kids don’t regress into autism until after 2 years of relatively normal development. The rest of the kids vary between these two extremes – the median age of regressive autism is around 18 months, long after thimerosal containing vaccines were last received for most kids. Making an association between ethyl mercury exposure a year earlier and autistic regression doesn’t make sense based on what we know about ethyl mercury.