Autism and Autism Spectrum Disorders and the Connection to Exposures to Perfluoroalkyl Chemicals
By
Robert Delaney
http://www.autism-pfos.net/
I think it is now well established that the rate of autism has been going up around the globe over at least the last 20 years (although there has been recent doubt cast on this because of a study done in England. Near the end of this write up, I discuss briefly why I think that the study is flawed.) I believe that there will soon be an overwhelming consensus that the cause of this increase is the result of a combination of genetic susceptibility and an environmental trigger or triggers. There are many possible environmental culprits from which to choose. Between 1,000 and 3,000 new chemicals come into use every year with virtually no toxicity testing requirements. Also, the industrial world and much of the developing world are seeing the rapid expansion of the use of electromagnetic signaling devices. Although there are many nasty neuro-developmental toxins in the environment, not many fit a few very basic requirements that would be needed in order to explain the rise in autism in so many diverse parts of the globe and in so many different cultural settings. Whatever the environmental trigger or triggers are, they have to meet at least these five criteria:
1. Their use must have expanded dramatically in the last 50 years. For instance, humans have been exposed to wood smoke for thousands of years and that exposure has been decreasing in the developed world. Mercury is a very nasty neurotoxin but like lead, PCBs, dioxins, DDT, and a host of pesticides, our exposures to these chemicals have been decreasing over the same time that the autism rate has been climbing. However, our use of cell phones, plastics, and other contaminants has been rising dramatically at the same time as autism rates have been rising.
2. Whatever the trigger or triggers are, they must be found around the globe at concentrations sufficient to affect diverse human populations. They must be found in diverse cultures where people live very different life styles. The autism rate is climbing in cultures as diverse as China, Sweden, Japan, the US, Australia, Spain, and Iceland. Rapidly increasing worldwide autism rates do not appear to be affected by climate, food sources, housing, clothing, etc. At least in the developed world, whatever the trigger is, we must all be exposed to it (autism rates cannot be determined in most of the third world because of a lack of data.)
3. Whatever the trigger or triggers are, their distribution must match a variety of autism cluster/distribution patterns. For instance, autism rates are higher along expressways, among the wealthier and more educated, in the US military, in people who shampoo their pets, etc. Although no population seems exempt from an increase in the rate of autism, there are many variations in the autism rate in subsets of various populations. The exposure patterns of people to the trigger or triggers need to match these variations in rates among subsets of populations.
4. Because of refined screening techniques, autism can be diagnosed at younger and younger ages, getting closer and closer to the birth of the child, indicating that whatever is triggering autism must be affecting the child while still in the womb. The trigger or triggers must be introduced into the uterus. In the November 2011 issue of Archives of General Psychiatry, two studies were released pointing to this conclusion as well. Whatever triggers autism must bypass (e.g., electromagnetic signaling) or pass through the placental barrier.
5. The trigger or triggers must be something that has been thought to have been benign.
Given this list of restrictions there are significantly fewer candidates for the trigger mechanism/mechanisms. The five most likely candidates as possible triggers appear to be:
· Chemicals associated with plastics,
· Chemicals associated with fire retardants,
· Perfluoroalkyl chemicals (PFCs),
· Silicone based chemicals, and
· Electromagnetic signaling (EM).
There are likely other candidates, but the research I completed to date does not indicate other candidates that could fit the profile. Chlorinated solvents, pesticides, PCB, PBBs, DDT, dioxins, heavy metals (such as lead and mercury) have all previously been identified as problem chemicals and huge efforts have been made to reduce exposures to them. The levels of these chemicals in our blood have generally been declining at roughly the same time that the autism rate has been rising, so none of them seem to be good candidates as ubiquitous triggers. Many other chemicals have not been around long enough or widely used enough, when compared to the five possible triggers mentioned above, to have caused such a widespread problem.
I have not done sufficient research on each of the five most likely factors listed above to definitively exclude any of them, but I do have reasons to suspect that the rate of manufacture and use of PFCs present the best match to the autism data and information available (based upon distribution, exposure, and autism cluster/distribution patterns). What I want to present is a weight of evidence explanation to support this association. Any one fact can easily be discounted in any number of ways. Some of what will be presented will come from well thought out, well researched studies. Other information will be very weak -- (for example, the autism rate in China has been reported to be increasing 20% per year. It is impossible to determine how this was calculated because China does not keep good records on the incidence of autism. However, there are other lines of evidence that indicate that the Chinese are becoming alarmed by the rise of autism in their country and that has implications for the discussion on PFCs as a possible trigger of autism.) Thus, the reader is advised to sift through the arguments and the literature for themselves.
The final disclaimer is that I am not a toxicologist, epidemiologist, medical doctor, or even a biologist. I fall into the generalist category when it comes to science (other than my familiarity with contaminant fate and transport in the environment). I don’t pretend to fully understand every article I cite. Again, it is a weight of evidence approach that I am taking and being a generalist is actually an advantage for such an approach.
PFCs come in many forms. The most easily recognized forms are Teflon® and ScotchGuard®, but it needs to be realized that these are just two out of thousands of consumer products that contain or have contained PFCs. I have only supplied the names of these two products to give the reader some context for what these compounds are. Also, there are at least 400 compounds that are classified as PFCs and there are literally thousands of manufacturers who either produce PFCs or use them in their products. In the literature however, the PFCs that are most commonly referred to are perfluorooctane sulfonate (PFOS) and perfluoroctanoic acid (PFOA). Most of the toxicological and epidemiological studies have been performed on these two contaminants as they are found the most frequently in the environment and in human blood serum. Also, many of the other PFCs eventually break down to form either PFOS or PFOA in nature and in humans. These PFOS/PFOA subunits generally will not break down further. A most important distinction between PFCs and other contaminants is that they tend to partition primarily to proteins rather than to fats or water. As proteins make up so much of the important systems of our cells and biochemistry, PFCs have the potential to negatively impact numerous processes in our bodies.
With minimal research on the internet, PFCs can be shown to match Items 1, 2, 4, and 5 above. They are found around the globe in human populations. They were invented in the 1940s and the uses of PFCs have steadily grown. They were thought to be biologically inactive and they pass the placental barrier. Meeting the criteria of Item 3 however is what, to a great extent, separates PFCs as a possible trigger mechanism from the other possible triggers mentioned above.
As was stated, PFCs were thought to be biologically inactive until around the 2000 when field studies began to show global contamination by PFCs and laboratory studies began to demonstrate significant toxicity in laboratory animals. The first question that must be asked about PFCs is whether they could be developmental neurotoxins. There are multiple studies that show the potential for PFCs to disrupt human neurodevelopment. The following are some examples:
· In vitro exposure to developing brain cells caused misdirected cell creation (the wrong cells developed when dividing brain cells were exposed to PFOS).10
· Laboratory mice and rats contaminated with PFCs experienced brain damage when exposed to ultra-sound.15, 16
· PFCs impact gene expression and proteins which may impact neurologic development.23, 25
This is not an effort to demonstrate that PFCs are a potent human neurotoxin at environmentally relevant concentrations. It is only to point out that PFCs do have the potential to impact neurodevelopment in humans. A great deal of research still needs to be done on the toxicity of PFCs. Polybrominated diethyl ethers (PBDEs - fire retardants) also show possible human neurotoxic effects and are fairly ubiquitous. That is why both families of chemicals are good suspects as trigger mechanisms. However, the possibility of being a human developmental neurotoxin is only one more piece of data in a weight of evidence analysis. As yet, I am not aware of any evidence of silicon based chemicals possibly being developmental neurotoxins, but that does not rule them out. Whatever the triggers of autism are, they have not previously been suspected of being highly toxic. Thus, PFCs, PBDEs, plasticizers, silicone-based chemicals, EM signals, or other possible causes must also be evaluated for neurotoxicity.
What follows is the “evidence” to consider when looking at PFCs as the possible trigger mechanism.
A) Autism is more prevalent among the wealthy and well educated in the United States57. PFC serum levels have been shown to be higher in Caucasians, the wealthy, and more educated1, 29, 44, 45, 46, 47. Caucasians are wealthier on average in America than their fellow citizens of African-American or Hispanic descent. The wealthier people are and the more educated they are, the more likely they are to eat more seafood (food sources with higher PFC contamination), buy new cars, buy high performance outerwear, buy electronics and computers, replace electronics and computers, replace carpets, replace treated flooring, repaint home interiors, replace treated furniture, and eat out more frequently. All of these behaviors expose the participants to higher levels of PFCs. Thus PFC exposure is higher in the wealthier Americans and more educated Americans and that coincides with higher rates of autism.
B) Autism rates are higher along expressways11. The main source of “non-point source” contamination of waterways by PFCs in Japan was found to be major transportation corridors12. PFCs are used in automotive lubricants, tires, wax, gaskets, hoses, windshield wiper fluids, fabrics, etc. PFCs are being released in substantial quantities from the transportation system. Thus, those who are the most exposed to transportation related pollution are also more likely exposed to higher levels of airborne PFCs.
C) Autism rates are higher among the offspring of the US military13. The US military uses large quantities of PFC-based fire suppressants and does extensive training with those fire suppressants. They are also early adopters of technology (e.g., electronics and computers), they have an emphasis on cleanliness, and they use high performance outerwear a great deal. They update their facilities, drive newer vehicles, and replace those vehicles frequently. Their equipment uses PFC-containing lubricants and hydraulic fuels. This has resulted in higher than average PFC exposure to the military personnel and their families and widespread PFC contamination of groundwater and surface water at military bases (personal experience).
D) Autism rates are higher in the children of people who shampoo their pets for fleas14. PFCs are used in shampoos and in pesticides. There is a pesticide that is usually associated with flea shampoos that is not a PFC. However, it partitions to the fats unlike PFCs. PFCs make excellent wetting solutions and getting pet shampoo to penetrate thick fur would likely lead to preferential the use of PFC containing products. PFCs as a surfactant are also reported to be gentle on skin as well.
E) Autism rates are among the highest in the nation in states with known widespread PFC contamination47, 48, 52. Minnesota and New Jersey which have documented high level PFC contamination in groundwater and drinking water, report some of the highest autism rates in the nation, with Minnesota often listed as the state with the highest autism rate in the nation. Minnesota is the home of 3M, the inventors many PFC formulations and was one of the major manufacturers of PFCs in the world.
Autism rates reported by various states are impacted by how statistics are kept, by how autism is reported, state awareness of the problem, etc. There is very little data on how extensive PFC contamination is in most states, so it is difficult to assess the relationship between the individual states’ autism rates and PFC contamination levels in people in those various states. Still, it is striking that Minnesota, the home of 3M and a state that has documented a high level of contamination in its waters and fish population would also be one of the leaders, if not the leader, in the occurrence of autism in the US.