Environmental toxicity as being associated with ASD in the exposed community

 

The problem with many studies concerning environmental toxicity is that they have great difficulty pointing a finger at a specific factor that is the cause.  For instance you may find there to be an excess of people driving silver cars that have autistic children but this might be due to their social class and hence their diet rather than the colour of the car itself.   As such specific toxins, animal models and specific sites are always useful to narrow down the toxic elements that are actually causing the damage.  Also, it is difficult to nail down as to whether any toxicity is actually active on the mother of the child or the ASD child itself. 

 

The most notable factor is that all the cases detoxified in an abnormal manner and that liver detoxification was always outside the normal range.  This appeared to be as if there was an overload to the system for detoxification and hence there was not surprising to find that there was excess of specific toxins in the blood in 16 of 18 ASD patients tested. 

 

The worry is that the overload comes from the gut in that there has been a demonstration of the absorption of compounds that would normally not be absorbed.  Hence the liver’s ability to remove the toxins may be inadequate and in some way a ‘leaky gut’ syndrome could cause toxins to produce long term damage to other systems of the body.  I.e. that removal of the toxin from the environment may have little effect in treatment once the ASD syndrome has been developed.  Also, many compounds that are taken from the environment, such as organochlorides, mercury or non-specific ones, may be involved in the toxicity. DDT molecule

 

One way that the researchers have looked at toxicity excretion is through the liver’s common action of attaching the toxin to a soluble glucose-derived compound  (e.g. glucaric acid) which will then allow the toxin to be excreted in the urine.   They found that there was a high level of glucaric acid in the urine, and low levels in the blood.  Also, sulphate may be used by the liver for the same procedure.  This is no longer being absorbed from the gut easily, and its manufacture in the body has changed and this explains why there are low levels of sulphate in the blood.  As a result it is as if the body’s ability of deal with toxins may well have been modified.                                                                                                                                    

Diagram 1 (right) DDT, an organochloride but one of the many that are present in the environment

Diagram 2: Glucaric acid

The proportion of ASD children that have an inadequate ability to detoxify environmental or dietary factors is unsure, although it seems to be high.  However, whatever cause is found for many cases of the condition, an explanation of this phenomenon must be included.

 

NB.  It is important to understand the changes in sulphate metabolism, the leaky gut syndrome, and gut pathology.

 

Nonspecific toxicity excess

 

Edelson SB, Cantor DS..  Autism: xenobiotic influences.  Toxicol Ind Health. 1998 Jul-Aug;14(4):553-63.  (Glucaric Acid Analysis, (2) blood analyses for identification of specific xenobiotic agents, and (3) Comprehensive Liver Detoxification Evaluation abnormal liver detoxification profiles in 20 autistic children.  Notably 100% of the autistic cases were outside the normal range).

 

Phase II Depression (S. Edelson, DAN Conference Sept, 1997, and Toxicology and Industrial Health 14 (4): 553-563 1998.

 

McGovern V. Autism and agricultural pesticides. Integrating data to track trends.  Environ Health Perspect. 2007 Oct;115(10):A504. However one group of pesticides did stand out: organochlorines, including the commonly used dicofol and endosulfan, were associated with ASD out to a maternal residential distance of 1,750-meter from the site of application. Dicofol and endosulfan, which are used in the production of cotton, fruit, vegetables, beans, and nuts, account for 98% of the organochlorines applied in the Central Valley region

Urinary increased sulphate (inorganic, organic), sulphite, thiocyanite (by about 50%) in autism vs control.  Also d-glucaric acid was very high, which is also used as a modifier for toxins.  Original source is not clear.  This can be got hold of through the web site: http://www.autismone.org/uploads/2007/James%20Adams%20AO%202007%20presentation% but has partly not been published.

 

Organochlorides and pesticides in the environment: association with autism

 

Roberts EM, English PB, Grether JK, Windham GC, Somberg L, Wolff C. Maternal residence near agricultural pesticide applications and autism spectrum disorders among children in the California Central Valley. Environ Health Perspect. 2007 Oct;115(10):1482-9. (ASD risk increased with the poundage of organochlorine applied and decreased with distance from field sites. CONCLUSIONS: The association between residential proximity to organochlorine pesticide applications during gestation and ASD among children should be further studied.)

 

Goldman LR, Koduru S. Chemicals in the environment and developmental toxicity to children: a public health and policy perspective. Environ Health Perspect. 2000 Jun;108 Suppl 3:443-8. (It simply suggests priority areas for research, including a large environmental prospective study of developmental neurotoxicity.  There is little specific data on individual chemicals etc.  The article uses valproate, thalidomide and genetics to justify the statement)

 

McGovern V.  Autism and agricultural pesticides. Integrating data to track trends.  Environ Health Perspect. 2007 Oct;115(10):A504. (see above)

 

Mercury  (see mercury under heavy metals)

 

Palmer RF, Blanchard S, Stein Z, Mandell D, Miller C Environmental mercury release, special education rates, and autism disorder: an ecological study of Texas. Health Place. Health Place. 2006 Jun;12(2):203-9.

 

Windham GC, Zhang L, Gunier R, Croen LA, Grether JK. Autism spectrum disorders in relation to distribution of hazardous air pollutants in the San Francisco bay area. Environ Health Perspect. 2006 Sep;114(9):1438-44.  Shows a potential association between amounts of airborn heavy metal and perhaps solvent pollutants.

 

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