SAN FRANCISCO, Oct. 19 (UPI) -- Many are counting on the numbers keepers to provide critical clues to some fundamental questions about the rising rates of autism diagnoses in America's children.
In particular, those who hold the mercury-based vaccine preservative thimerosal responsible for the increase have been eagerly awaiting a verdict on their prediction that as children's exposure to the compound decreases, so, too, will their autism rates.
Phased out of most childhood shots around the turn of the century, thimerosal remains in some booster and flu vaccines recommended for pregnant women and babies.
With the release of California's special-education statistics in the summer of 2005, the thimerosal skeptics gleaned a glimmer of substantiation of their suspicions.
In a trend they had anticipated, a decade-long climb of newly identified autism cases indeed appeared to be turning around at the critical juncture.
The data were compiled by the state Department of Developmental Services. They showed the sum total of autistic children in the system continues to grow -- by now topping 28,000. However, the rate of increase peaked in 2002 -- the year the government says the last of the thimerosal-containing childhood vaccines expired -- then started to take a slight dip.
The telling parallels were highlighted in a 2006 study by geneticists Dr. Mark Geier and David Geier, a father-son research team often cited by mercury-in-medicine opponents.
They picked up signs of a downward drift in neurodevelopmental disorder cases from mid-2002 through 2005 in both the figures released by the California agency, widely regarded as the most accurate barometer of full-syndrome, professionally diagnosed cases, and the much less reliable federal Vaccine Adverse Events Reporting System.
The latter is a depository of voluntarily submitted, unsubstantiated claims of ill effects thought to be related to immunization.
While acknowledging the loosely structured program is short on consistency and credibility, the Geiers included it as an informal confirmation of the California counts.
In addition, they cited provisional national education department data showing a concurrent decrease of 529 in the number of new autism diagnoses recorded among children ages 3 to 5 after years of annual increases.
There were 1,451 new cases in 2001-2002; 1,981 in 2002-2003; 3,707 in 2003-2004; and 3,178 in 2004-2005.
The Geiers attributed the rise and fall of autism diagnoses to the corresponding trends in the use of thimerosal-containing vaccines.
Those who disagree point to a new set of figures released last month by California's DDS, which show a recent upturn in the state's caseload of autistic children 3 to 5 years old -- from a total of 6,083 reported at the end of the second quarter, in June, to 6,188 as of the end of the third quarter, in September.
If thimerosal is to blame, why are the numbers going up, they ask?
However, others think the removal of the compound from childhood vaccines has been offset by its continued presence in flu shots administered to infants and pregnant women whose developing fetuses are more vulnerable to the effects of mercury than are children already born.
Others read far less into the numbers. Even setting aside the inherent imprecision of using raw counts -- which any number of fluctuating factors such as falling birth rates can affect -- as a measure of trends in prevalence, there are other confounding elements to consider.
The California DDS itself prefaced its reports with a cautionary note, stating, "(I)t is inaccurate to represent the change in the numbers reported from one quarter to the next as 'new intakes.'"
The caveat: A recorded hike from one period to the next does not necessarily represent new arrivals.
The reasons for this disappointingly confounding revelation include the sometimes years-long delay in the filing of an evaluation. The newly recorded may indeed be those coming into the system for the first time, but they could also be old-timers whose paperwork hadn't caught up with them.
Similarly, a gap may exist between those said to depart the programs and those who actually do.
Even if the waning caseload numbers in the earlier California report represented a true downward trend in actual autism rates, there remain other uncertainties that could stand in the way of connecting the dots directly to vaccines.
Take a March 2006 study showing newborns may be 65 to 130 times more sensitive than adults -- and even 26 to 50 times more vulnerable than fellow infants -- to certain pesticides. This variability is far greater than anyone had predicted.
Based on previous presumptions -- which the findings take to task, at least for the chemicals in question -- Environmental Protection Agency standards require that in cases where individual susceptibilities are not well known, levels of exposure considered safe for adults should be multiplied by a factor of 10 as an extra precaution to protect the more vulnerable younger populations.
The new study -- which suggests that factor should be six to 13 times greater -- raises questions about whether children are sufficiently safeguarded under the current safety criteria for pesticide exposure.
At the very least, more research is needed to find out whether that's the case, the authors say.
What makes the findings potentially relevant to the autism debate is that the chemicals under study, so-called organophosphate compounds like diazinon and chlorpyrifos, have been shown, in high doses, to have profound effects on the central nervous system.
Growing evidence from animal and human studies also suggests chronic low-level exposure may affect neurodevelopment.
What makes the tale even more intriguing is that to guard children's health, the pesticides were banned from home use in 2001 -- about the time the last of the thimerosal-containing childhood vaccines were reaching the end of their run.
And just as with the mercury-based preservative, which remains in some flu and booster shots, so too the chemicals are still permitted for agricultural and certain structural purposes, such as treatment of house foundations.
Of course, the compounds may have nothing to do with autism, but the parallels are suggestive, and the findings illustrate how both sides of the thimerosal issue can rightly claim to be making certain valid points.
They lend support to those who insist vaccine trends are not the only ones that can explain the perceived patterns of harm as well as to those who question the establishment's capability to safeguard children from it.
In fact, researchers probing the mercurial chemical that has escaped much scientific scrutiny for over 60 years have dug up evidence that indicates the nation's leading health authorities examined the wrong compound and failed to look far enough when they were assessing the danger posed by thimerosal in vaccines.
(Note: In this multi-part installment, based on dozens of reports, conferences and interviews, Ped Med is keeping an eye on autism, taking a backward glance at its history and surrounding controversies, facing facts revealed by research and looking forward to treatment enhancements and expansions.)
Next: Looking for safety standards in all the wrong places
--
UPI Consumer Health welcomes comments on this column. E-mail: [email protected]
