New California Study on Children’s Blood Mercury Levels Leaves Unanswered Questions About Mercury’s Role in Autism.
SafeMinds Calls for Studies on Early Exposures and Altered Mercury Susceptibility, End to Mercury in Influenza Vaccines.
Monday, October 19, 2009 – The science journal Environmental Health Perspectives released findings from the Childhood Autism Risks from Genetics and the Environment (CHARGE) Study comparing blood mercury levels in children with and without an autism spectrum disorder. The study looked only at the recent exposures reflected in blood mercury concentrations. It found that current blood mercury levels were lower in the autism group and, given equivalent exposures, blood levels were the same relative to typical children. It observed that blood levels in the typical group were comparable to those reported in the large CDC NHANES study. The authors were careful to note that the study did not investigate and was therefore unable to determine whether earlier exposures played a role in autism onset or whether the group with autism had increased susceptibility to the mercury exposures, regardless of when the exposure occurred.
The study, Blood Mercury Concentrations in Children with and without Autism, was funded by the National Institute of Environmental Health Sciences and lead by Irva Hertz-Picciotto at the University of California-Davis. Autism onset has been linked to mercury exposure occurring prior to diagnosis. This study was designed to examine whether autistic children might have higher on-going exposures that might increase the severity of the condition post-diagnosis. It also sought to determine if blood mercury concentrations might be different in autism even at equivalent exposures, suggesting altered toxicokinetics of mercury in autistic children once exposed. The authors were explicit in the paper to note that the study was not designed to examine whether exposures prior to diagnosis were higher in the autistic group, whether autistic children might have a unique susceptibility to the toxic effects of mercury, or whether some aspects of toxicokinetics other than those reflected in blood measurements are different in those with autism.
Blood mercury levels in all children in the study are noteworthy, as they correspond to levels found in the nationally representative NHANES study for children 1-5 years old (CDC, 2004). A recent analysis of NHANES reported that chronic mercury exposure is on the rise from all sources (Laks, 2009). “The CHARGE findings are another indication that we should be alarmed about ongoing mercury exposures to Americans, and especially to children and fetuses, who are most susceptible to mercury’s effects,” said Ms. Bernard. “We should be eliminating mercury regardless of where it comes from, whether from fish, ambient air, or dental amalgams.”
Research has demonstrated that certain subgroups, including children with autism, show potentially higher susceptibility to environmental stressors like mercury (James, 2009; Ralston, 2008; Sajdel-Sulkowska, 2009). Some recent studies have indicated increased mercury in tissues and organs of people with autism relative to controls (Adams, 2007; Sajdel-Sulkowska, 2009; Desoto, 2007; Desoto, 2008). Given equivalent exposures, as indicated by the CHARGE study, SafeMinds feels that it is imperative that research is conducted that investigates altered handling of mercury in those with autism.
SafeMinds calls the continued use of mercury in H1N1 and seasonal influenza vaccines recommended for pregnant women and children a tragic error in judgment on the part of the CDC. “The mercury-free alternatives should be given preference in vaccine recommendations for these susceptible groups,” said Ms. Bernard.
SafeMinds is a charitable non-profit and leader in funding and advancing the science regarding mercury exposure as it relates to autism. Our expertise extends beyond mercury-related exposures to broader vaccine safety issues, due to many Board Members holding government agency committee positions such as the Interagency Autism Coordinating Committee, various CDC Vaccine Committees, the Department of Defense Autism Spectrum Disorder Research Program and the National Vaccine Advisory Committee’s Vaccine Safety Working Group.
Laks DR . Assessment of chronic mercury exposure within the U.S. population, National Health and Nutrition Examination Survey, 1999-2006. Biometals. 2009 Aug 21. [Epub ahead of print]
CDC. Blood mercury levels in young children and childbearing-aged women—United States, 1999-2002. MMWR 2004; 53:1018-1020. http://www.cdc.gov/mmwr/PDF/wk/mm5343.pdf
James SJ, Rose S, Melnyk S, Jernigan S, Blossom S, Pavliv O, Gaylor DW. Cellular and mitochondrial glutathione redox imbalance in lymphoblastoid cells derived from children with autism. FASEB J. 2009 Aug;23(8):2374-83. Epub 2009 Mar 23.
Ralston NV, Ralston CR, Blackwell JL 3rd, Raymond LJ. Dietary and tissue selenium in relation to methylmercury toxicity. Neurotoxicology. 2008 Sep;29(5):802-11. Epub 2008 Aug 9.
Adams JB, Romdalvik J, Ramanujam VM, Legator MS. Mercury, lead, and zinc in baby teeth of children with autism versus controls. J Toxicol Environ Health A. 2007 Jun;70(12):1046-51.
Sajdel-Sulkowska EM, Xu M, Koibuchi N. Increase in cerebellar neurotrophin-3 and oxidative stress markers in autism. Cerebellum. 2009 Sep;8(3):366-72. Epub 2009 Apr 9.
DeSoto MC. A reply to Soden et al.: your data shows autistic children have higher levels of heavy metals.
Clin Toxicol (Phila). 2008 Dec;46(10):1098; author reply 1098.
Desoto MC, Hitlan RT. Blood levels of mercury are related to diagnosis of autism: a reanalysis of an important data set. J Child Neurol. 2007 Nov;22(11):1308-11.