Thimerosal and autism? A plausible hypothesis that should not be dismissed

Fetal origins of autism spectrum disorders: the non-associated maternal factors

Aim:

Several population-based studies have been conducted to determine whether maternal exposures are involved in the pathophysiology of autism spectrum disorder (ASD). We review these studies and describe the factors not associated with increased risk for ASD development.

Methods:

We identified studies describing associations between maternal exposures and ASD development. These studies include the Childhood Autism Risks from Genetics and the Environment, Nurses’ Health Study II, and the Swedish population registry.

Results:

Factors not associated with ASD development include Type 2 and gestational diabetes, chronic hypertension, fever treated with antipyretic medication, autoimmune disease and short interpregnancy intervals.

Conclusion:

There is increasing evidence that maternal exposures are involved in the pathophysiology of ASD in the developing fetus.

Lay Abstract: Autism spectrum disorder currently affects one in 68 children in the USA, with up to one in 42 boys. Its underlying etiology is largely unknown. Although autism was once considered a childhood disease, efforts for early detection led to the realization that it might originate at a much earlier stage, namely fetal life. Several maternal risk factors have recently been studied to establish associations with autism in the offspring. In this review, we present the maternal risk factors that were not found to have such associations.

Abnormalities in the zinc-metalloprotease-BDNF axis may contribute to megalencephaly and cortical hyperconnectivity in young autism spectrum disorder patients

Whereas aberrant brain connectivity is likely the core pathology of autism-spectrum disorder (ASD), studies do not agree as to whether hypo- or hyper-connectivity is the main underlying problem. Recent functional imaging studies have shown that, in most young ASD patients, cerebral cortical regions appear hyperconnected, and cortical thickness/brain size is increased. Collectively, these findings indicate that developing ASD brains may exist in an altered neurotrophic milieu. Consistently, some ASD patients, as well as some animal models of ASD, show increased levels of brain-derived neurotrophic factor (BDNF). However, how BDNF is upregulated in ASD is unknown. To address this question, we propose the novel hypothesis that a putative zinc-metalloprotease-BDNF (ZMB) axis in the forebrain plays a pivotal role in the development of hyperconnectivity and megalencephaly in ASD. We have previously demonstrated that extracellular zinc at micromolar concentrations can rapidly increase BDNF levels and phosphorylate the receptor tyrosine kinase TrkB via the activation of metalloproteases. The role of metalloproteases in ASD is still uncertain, but in fragile X syndrome, a monogenic disease with an autistic phenotype, the levels of MMP are increased. Early exposure to lipopolysaccharides (LPS) and other MMP activators such as organic mercurials also have been implicated in ASD pathogenesis. The resultant increases in BDNF levels at synapses, especially those involved in the zinc-containing, associative glutamatergic system may produce abnormal brain circuit development. Various genetic mutations that lead to ASD are also known to affect BDNF signaling: some down-regulate, and others up-regulate it. We hypothesize that, although both up- and down-regulation of BDNF may induce autism symptoms, only BDNF up-regulation is associated with the hyperconnectivity and large brain size observed in most young idiopathic ASD patients. To test this hypothesis, we propose to examine the ZMB axis in animal models of ASD. Synaptic zinc can be examined by fluorescence zinc staining. MMP activation can be measured by in situ zymography and Western blot analysis. Finally, regional levels of BDNF can be measured. Validating this hypothesis may shed light on the central pathogenic mechanism of ASD and aid in the identification of useful biomarkers and the development of preventive/therapeutic strategies.

Transcriptomic analyses of neurotoxic effects in mouse brain after intermittent neonatal administration of thimerosal

Thimerosal is a vaccine antimicrobial preservative which has long been suspected an iatrogenic factor possibly contributing to neurodevelopmental disorders including autism. The association between infant vaccine thimerosal exposure and autism remains an open question. Although thimerosal has been removed from mandatory childhood vaccines in the United States, thimerosal-preserved vaccines are still widely used outside of the United States especially in developing countries. Notably, thimerosal-containing vaccines are being given to the newborns within the first 12-24 h after birth in some countries. To examine the possible neurotoxic effects of early neonatal exposure to a higher level of thimerosal, FVB mice were subcutaneously injected with thimerosal-mercury at a dose which is 20× higher than that used for regular Chinese infant immunization during the first 4 months of life. Thimerosal-treated mice exhibited neural development delay, social interaction deficiency, and inclination of depression. Apparent neuropathological changes were also observed in adult mice neonatally treated with thimerosal. High-throughput RNA sequencing of autistic-behaved mice brains revealed the alternation of a number of canonical pathways involving neuronal development, neuronal synaptic function, and the dysregulation of endocrine system. Intriguingly, the elevation of anterior pituitary secreting hormones occurred exclusively in male but not in female thimerosal-treated mice, demonstrating for the first time the gender bias of thimerosal-mercury toxicity with regard to endocrine system. Our results indicate that higher dose of neonatal thimerosal-mercury (20× higher than that used in human) is capable of inducing long-lasting substantial dysregulation of neurodevelopment, synaptic function, and endocrine system, which could be the causal involvements of autistic-like behavior in mice.

Personalization of multiple sclerosis treatments: using the chelation therapy approach

Though Multiple Sclerosis (MS) sufferers are probably genetically predisposed, toxic metal poisoning (TMP) does seem an increasingly likely environmental trigger. The technique for measuring and clearing TMP was chelation therapy using ethylene-diamine-tetracetic acid (EDTA), which revealed aluminum accumulation in both cases. The first patient, initially benefiting from removing dental fillings that had leaked mercury, also showed gadolinium accumulation from scan contrast medium, and a genomic deficiency of glutathione transferase M1. Glutathione production was impaired and hence also liver detoxification functions. The personal protocol involved glutathione administration and deutrosulfazyme to enhance oxygenation and alleviate oxidative stress. As aluminum began to clear with EDTA infusion, the extracellular/intracellular water ratio was carefully monitored, and carbohydrates limited. In the second case, aluminum poisoning responded to EDTA chelation therapy with eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA), multivitamins, and glutathione administration, again followed by deutrosulfazyme, water ratio control, and dietary correction. The two personalized protocols presented here tend to confirm the hypothesis of TMP as an environmental or iatrogenic trigger for MS, especially when inadequate detoxification lies at the root. Cleansing by chelation therapy, properly understood, can be efficacious, especially bearing in mind the altered cellular water ratio.

Autism spectrum disorder phenotypes and prenatal exposure to methylmercury

BACKGROUND

There continues to be public concern that mercury exposure and autism spectrum disorder (ASD) may be associated. The primary source of exposure to organic mercury in humans is to methylmercury from fish consumption. We evaluated the association between prenatal methylmercury exposure and ASD phenotype in children and adolescents in the Republic of Seychelles, where fish consumption is high.

METHODS

We administered the Social Communication Questionnaire to parents of a cohort of 1784 children, adolescents, and young adults. The Social Responsiveness Scale was administered to teachers of 537 cohort subjects at about 10 years of age. Prenatal exposure to methylmercury was measured in maternal hair samples collected at or near the time of birth. Multivariable regression models evaluated the relationship between prenatal methylmercury exposure and ASD phenotypic scores, adjusting for relevant covariates.

RESULTS

The mean prenatal methylmercury exposure for subjects in the analysis was 8.4 ppm (standard deviation [SD] = 5.7). The mean Social Communication Questionnaire score was 8.0 (SD = 4.4). The mean prenatal methylmercury exposure for subjects with Social Responsiveness Scale scores was 6.7 ppm (SD = 4.4) and the mean Social Responsiveness Scale score was 57.6 (SD = 26.8). No consistent association between prenatal methylmercury exposure and ASD screening instrument was found, using linear and nonlinear regression analyses.

CONCLUSIONS

Prenatal exposure to methylmercury was not associated with ASD phenotypic behaviors in our cohort of high fish consumers. Our findings contribute to the growing literature suggesting that exposure to methylmercury does not play an important role in the development of ASD phenotypic behavior.

A comparison of urinary mercury between children with autism spectrum disorders and control children

Background

Urinary mercury concentrations are used in research exploring mercury exposure. Some theorists have proposed that autism is caused by mercury toxicity. We set out to test whether mercury concentrations in the urine of children with autism were significantly increased or decreased compared to controls or siblings.

Methods

Blinded cohort analyses were carried out on the urine of 56 children with autism spectrum disorders (ASD) compared to their siblings (n = 42) and a control sample of children without ASD in mainstream (n = 121) and special schools (n = 34).

Results

There were no statistically significant differences in creatinine levels, in uncorrected urinary mercury levels or in levels of mercury corrected for creatinine, whether or not the analysis is controlled for age, gender and amalgam fillings.

Conclusions

This study lends no support for the hypothesis of differences in urinary mercury excretion in children with autism compared to other groups. Some of the results, however, do suggest further research in the area may be warranted to replicate this in a larger group and with clear measurement of potential confounding factors.

BISTABLE EQUILIBRIUM POINTS OF MERCURY BODY BURDEN

In the last century, mercury levels in the global environment have tripled as a result of increased pollution from industrial, occupational, medicinal and domestic uses.1 Glutathione is known to be the main agent responsible for the excretion of mercury (Refs. 2 to 4). It has also been shown that mercury inhibits glutathione synthetase (an enzyme acting in the synthesization of glutathione), therefore leading to decreased glutathione levels (Refs. 5 to 7). Mercury also interferes with the production of heme in the porphyrin pathway.8 Heme is needed for biological energy production and ability to detox organic toxins via the P450 enzymes.9 The purpose of this paper is to show that the body's response to mercury exposure is hysteretic, i.e. when this feedback of mercury on its main detoxifying agents is strong enough, then mercury body burden has two points of equilibrium: one with normal abilities to detoxify and low levels of mercury and one with inhibited abilities to detoxify and high levels of mercury. Furthermore, a small increase of the body's mercury burden may not be sufficient to trigger observable neurotoxic effects but it may be sufficient to act as a switch leading to an accumulation of mercury in the body through environmental exposure until its toxicity is manifested.

Evaluation of oxidative stress in autism: defective antioxidant enzymes and increased lipid peroxidation

Autism is a neurodevelopmental disorder of childhood with poorly understood etiology and pathology. This pilot study aims to evaluate the levels of antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and levels of malondialdehyde (MDA), a marker of lipid peroxidation, in Egyptian autistic children. Autism is a neurodevelopmental disorder of childhood with poorly understood etiology and pathology. The present study included 20 children with autism diagnosed by DSM-IV-TR criteria and Childhood Autism Rating Scale. Controls included 25 age-matched healthy children. Cases were referred to Outpatient Clinic of Children with Special Needs Department, National Research Center, Cairo, Egypt. We compared levels of SOD, GSH-Px, and MDA in children with autism and controls. In children less than 6 years of age, levels of SOD, and GSH-Px were significantly lower in autistic children compared with their controls, while MDA was significantly higher among patients than controls. In children older than 6 years, there was no significant difference in any of these values between cases and controls. We concluded that children with autism are more vulnerable to oxidative stress in the form of increased lipid peroxidation and deficient antioxidant defense mechanism especially at younger children. We highlight that autistic children might benefit from antioxidants supplementation coupled with polyunsaturated fatty acids. Moreover, early assessment of antioxidant status would have better prognosis as it may decrease the oxidative stress before inducing more irreversible brain damage.

The plausibility of a role for mercury in the etiology of autism: a cellular perspective

Autism is defined by a behavioral set of stereotypic and repetitious behavioral patterns in combination with social and communication deficits. There is emerging evidence supporting the hypothesis that autism may result from a combination of genetic susceptibility and exposure to environmental toxins at critical moments in development. Mercury (Hg) is recognized as a ubiquitous environmental neurotoxin and there is mounting evidence linking it to neurodevelopmental disorders, including autism. Of course, the evidence is not derived from experimental trials with humans but rather from methods focusing on biomarkers of Hg damage, measurements of Hg exposure, epidemiological data, and animal studies. For ethical reasons, controlled Hg exposure in humans will never be conducted. Therefore, to properly evaluate the Hg-autism etiological hypothesis, it is essential to first establish the biological plausibility of the hypothesis. This review examines the plausibility of Hg as the primary etiological agent driving the cellular mechanisms by which Hg-induced neurotoxicity may result in the physiological attributes of autism. Key areas of focus include: (1) route and cellular mechanisms of Hg exposure in autism; (2) current research and examples of possible genetic variables that are linked to both Hg sensitivity and autism; (3) the role Hg may play as an environmental toxin fueling the oxidative stress found in autism; (4) role of mitochondrial dysfunction; and (5) possible role of Hg in abnormal neuroexcitory and excitotoxity that may play a role in the immune dysregulation found in autism. Future research directions that would assist in addressing the gaps in our knowledge are proposed.

Safety review: squalene and thimerosal in vaccines

Few studies show the reluctance of the people to get vaccinated against A (H1N1) influenza for fear of side effects of squalene (MF59, AS03, AF03) and thimerosal. The aim of this paper is to assess the safety in using these adjuvants and preservative reviewing data of clinical trials relative to which formulation includes these compounds. In the current state of knowledge, these vaccines have proved to be effective even though they more frequently give local adverse events than non-adjuvanted influenza vaccines. Systemic side effects are generally not serious. In the studies, adjuvanted vaccines do not increase neither the risk of Guillain Barre syndrome nor auto-immune diseases. There is no convincing evidence that exposure to thimerosal in vaccines had any deletorious effect on physiological outcome.

Porphyrinuria in Korean children with autism: correlation with oxidative stress

Autism spectrum disorder (ASD) is a neurodevelopmental disorder believed to be associated with heavy metal exposure, especially mercury (Hg), and is characterized by disturbances in metal elimination. Various studies correlated elevated heavy metal body burden with ASD diagnoses as evidenced by increased urinary porphyrin levels in patients. Urinary porphyrins were also determined in Korean patients diagnosed with ASD (n = 65) who visited AK Eastern Medicinal Clinic in Kangnam-gu, Seoul, from June 2007 to September 2008, compared to controls (n = 9) residing in the same area, by means of Metametrix (CLIA-approved) laboratory testing. Further, urinary organic acids as indicators of hepatic detoxification/oxidative stress were also analyzed among patients diagnosed with ASD. Significant increases were found in patients diagnosed with ASD for proporphyrins, pentacarboxyporphyrin, precoproporphyrin, coproporphyrins, and total porphyrins. Significant correlations were observed between hepatic detoxification/oxidative stress markers and urinary porphyrins. In agreement with published data, the present results demonstrated that measurement of porphyrins serves as a reliable tool for diagnosis of heavy metal involvement in ASD.

A prospective study of thimerosal-containing Rho(D)-immune globulin administration as a risk factor for autistic disorders

BACKGROUND

This study evaluated the relationship between prenatal mercury exposure from thimerosal (49.55% mercury by weight)-containing Rho(D)-immune globulins (TCRs) and autism spectrum disorders (ASDs).

METHODS

The Institutional Review Board of the Institute for Chronic Illnesses approved the present study. A total of 53 consecutive non-Jewish Caucasian patients with ASDs (Diagnostic and statistical manual of mental disorders, fourth ed. - DSM IV) born between 1987 and 2001 who presented to the Genetic Centers of America for outpatient genetic/developmental evaluations were prospectively collected from June 1, 2005 through March 31, 2006. Imaging and laboratory testing were conducted on each patient to rule out other causal factors for their ASDs. As race-matched controls, the frequency of Rh negativity was determined from 926 non-Jewish Caucasian pregnant women who had presented for outpatient prenatal genetics care to the Genetic Centers of America between 1980 and 1989.

RESULTS

Children with ASDs (28.30%) were significantly more likely (odds ratio 2.35, 95% confidence interval 1.17-4.52, p < 0.01) to have Rh-negative mothers than controls (14.36%). Each ASD patient's mother was determined to have been administered a TCR during her pregnancy.

CONCLUSION

The results provide insights into the potential role prenatal mercury exposure may play in some children with ASDs.

Maternal Rh D status, anti-D immune globulin exposure during pregnancy, and risk of autism spectrum disorders

OBJECTIVE

The objective of the study was to investigate the association between maternal Rh D status, prenatal exposure to anti-D immune globulin, and the risk of autism in the offspring.

STUDY DESIGN

Case-control study among children born from 1995 to 1999 at Kaiser Permanente Northern California hospitals. Cases (n = 400) were children with an autism diagnosis; controls (n = 410) were children without autism, randomly sampled and frequency matched to cases on sex, birth year, and birth hospital. Maternal Rh D status and anti-D immune globulin exposure were ascertained from prenatal medical records.

RESULTS

No case-control differences were observed for maternal Rh negative status (11.5% vs 10.0%, P = .5) or prenatal anti-D immune globulin exposure (10.0% vs. 9.3%, P = .7). Risk of autism remained unassociated with maternal Rh status or prenatal exposure to anti-D immune globulins after adjustment for covariates.

CONCLUSION

These data support previous findings that prenatal exposure to thimerosal-containing anti-D immune globulins does not increase the risk of autism.

Molecular structures of thimerosal (Merthiolate) and other arylthiolate mercury alkyl compounds

The molecular structure of sodium ethylmercury thiosalicylate (also known as thimerosal and Merthiolate) and related arylthiolate mercury alkyl compounds, namely PhSHgMe and PhSHgEt, have been determined by single crystal X-ray diffraction. (1)H NMR spectroscopic studies indicate that the appearance of the (199)Hg mercury satellites of the ethyl group of thimerosal is highly dependent on the magnetic field and the viscosity of the solvent as a consequence of relaxation due to chemical shift anisotropy.

Developmental regression and autism reported to the Vaccine Adverse Event Reporting System

We report demographic and clinical characteristics of children reported to the US Vaccine Adverse Event Reporting System (VAERS) as having autism or another developmental disorder after vaccination. We completed 124 interviews with parents and reviewed medical records for 31 children whose records contained sufficient information to evaluate the child's developmental history. Medical record review indicated that 27 of 31 (87%) children had autism/ASD and 19 (61.3%) had evidence of developmental regression (loss of social, language, or motor skills). The proportion of VAERS cases of autism with regression was greater than that reported in population-based studies, based on the subset of VAERS cases with medical record confirmation. This difference may reflect preferential reporting to VAERS of autism with regression. In other respects, the children in this study appear to be similar to other children with autism. Further research might determine whether the pathogenesis of autism with developmental regression differs from that of autism without regression.

Identification and evaluation of children with autism spectrum disorders

Autism spectrum disorders are not rare; many primary care pediatricians care for several children with autism spectrum disorders. Pediatricians play an important role in early recognition of autism spectrum disorders, because they usually are the first point of contact for parents. Parents are now much more aware of the early signs of autism spectrum disorders because of frequent coverage in the media; if their child demonstrates any of the published signs, they will most likely raise their concerns to their child's pediatrician. It is important that pediatricians be able to recognize the signs and symptoms of autism spectrum disorders and have a strategy for assessing them systematically. Pediatricians also must be aware of local resources that can assist in making a definitive diagnosis of, and in managing, autism spectrum disorders. The pediatrician must be familiar with developmental, educational, and community resources as well as medical subspecialty clinics. This clinical report is 1 of 2 documents that replace the original American Academy of Pediatrics policy statement and technical report published in 2001. This report addresses background information, including definition, history, epidemiology, diagnostic criteria, early signs, neuropathologic aspects, and etiologic possibilities in autism spectrum disorders. In addition, this report provides an algorithm to help the pediatrician develop a strategy for early identification of children with autism spectrum disorders. The accompanying clinical report addresses the management of children with autism spectrum disorders and follows this report on page 1162 [available at www.pediatrics.org/cgi/content/full/120/5/1162]. Both clinical reports are complemented by the toolkit titled "Autism: Caring for Children With Autism Spectrum Disorders: A Resource Toolkit for Clinicians," which contains screening and surveillance tools, practical forms, tables, and parent handouts to assist the pediatrician in the identification, evaluation, and management of autism spectrum disorders in children.

A prospective study of mercury toxicity biomarkers in autistic spectrum disorders

Porphyrins are derivatives formed in the heme synthesis pathway and porphyrins afford a measure of xenobiotic exposure. The steps in the heme pathway most vulnerable to heavy metal inhibition are uroporphyrin decarboxylase (UROD) and coproporphyrinogen oxidase (CPOX) reactions. Mercury toxicity was associated with elevations in urinary coproporphyrin (cP), pentacarboxyporphyrin (5cxP), and precoproporphyrin (prcP) (also known as keto-isocoproporphyrin) levels. Two cohorts of autistic patients in the United States and France had urine porphyrin levels associated with mercury toxicity. A prospective study of urinary porphyrin testing at LabCorp (United States) and the Laboratoire Philippe Auguste (France) involving 71 autism spectrum disorder (ASD) patients, neurotypical sibling controls, and general population controls was undertaken. ASD patients had significant elevations in urinary levels of cP, 5cxP, and prcP relative to controls, and > 50% of ASD patients had urinary cP levels more than 2 standard deviations above the mean values for neurotypical sibling controls. Significant reductions in urinary 5cxP and cP levels were observed in ASD patients following chelation. A significant correlation was found between urinary porphyrins measured at LabCorp and those measured at the Laboratoire Philippe Auguste on individual ASD patients. The established developmental neurotoxicity attributed to mercury and biochemical/genomic evidence for mercury susceptibility/toxicity in ASDs indicates a causal role for mercury. Urinary porphyrin testing is clinically available, relatively inexpensive, and noninvasive. Porphyrins need to be routinely measured in ASDs to establish if mercury toxicity is a causative factor and to evaluate the effectiveness of chelation therapy.

Update on the National Vaccine Injury Compensation Program

The National Childhood Vaccine Injury Act of 1986, as amended, established the Vaccine Injury Compensation Program (VICP). The VICP went into effect on October 1, 1988 and is a Federal "no-fault" system designed to compensate individuals, or families of individuals, who have been injured by covered vaccines. From 1988 until July 2006, a total of 2531 non-autism/thimerosal and 5030 autism/thimerosal claims were made to the VICP. The compensation paid for the non-autism/thimerosal claims from 1988 until 2006 was $902,519,103.37 for 2542 awards. There was no compensation for any of the autism/thimerosal claims. On the basis of the deaths and extensive suffering to patients and families from the adverse reactions to vaccines, all physicians must provide detailed information in the Vaccine Information Statement to the patient or the parent or legal guardian of the child about the potential dangers of vaccines as well as the VICP.

A case series of children with apparent mercury toxic encephalopathies manifesting with clinical symptoms of regressive autistic disorders

Impairments in social relatedness and communication, repetitive behaviors, and stereotypic abnormal movement patterns characterize autism spectrum disorders (ASDs). It is clear that while genetic factors are important to the pathogenesis of ASDs, mercury exposure can induce immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with ASDs. The Institutional Review Board of the Institute for Chronic Illnesses (Office for Human Research Protections, U.S. Department of Health and Human Services, IRB number IRB00005375) approved the present study. A case series of nine patients who presented to the Genetic Centers of America for a genetic/developmental evaluation are discussed. Eight of nine patients (one patient was found to have an ASD due to Rett's syndrome) (a) had regressive ASDs; (b) had elevated levels of androgens; (c) excreted significant amounts of mercury post chelation challenge; (d) had biochemical evidence of decreased function in their glutathione pathways; (e) had no known significant mercury exposure except from Thimerosal-containing vaccines/Rho(D)-immune globulin preparations; and (f) had alternate causes for their regressive ASDs ruled out. There was a significant dose-response relationship between the severity of the regressive ASDs observed and the total mercury dose children received from Thimerosal-containing vaccines/Rho (D)-immune globulin preparations. Based upon differential diagnoses, 8 of 9 patients examined were exposed to significant mercury from Thimerosal-containing biologic/vaccine preparations during their fetal/infant developmental periods, and subsequently, between 12 and 24 mo of age, these previously normally developing children suffered mercury toxic encephalopathies that manifested with clinical symptoms consistent with regressive ASDs. Evidence for mercury intoxication should be considered in the differential diagnosis as contributing to some regressive ASDs.

Mercury exposure and public health

Mercury is a metal that is a liquid at room temperature. Mercury has a long and interesting history deriving from its use in medicine and industry, with the resultant toxicity produced. In high enough doses, all forms of mercury can produce toxicity. The most devastating tragedies related to mercury toxicity in recent history include Minamata Bay and Niagata, Japan in the 1950s, and Iraq in the 1970s. More recent mercury toxicity issues include the extreme toxicity of the dimethylmercury compound noted in 1998, the possible toxicity related to dental amalgams, and the disproved relationship between vaccines and autism related to the presence of the mercury-containing preservative, thimerosal.

A prospective assessment of porphyrins in autistic disorders: a potential marker for heavy metal exposure

Autism was recently associated with a urinary porphyrin pattern indicative of mercury toxicity in a large cohort of French children. The IRB of the Institute for Chronic Illnesses approved the present study. A total of 37 consecutive American patients (> or = 7 years-old) with autism spectrum disorders (ASDs) (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-DSM IV), born from 1983-1998, that presented to the Genetic Centers of America for outpatient genetic evaluations were prospectively examined for urinary prophryin levels (LabCorp, Inc.) from June 2005-June 2006. Imaging and laboratory testing were conducted on each patient to rule-out other causal factors for their ASDs. As controls, age-, sex-, and race-matched neurotypical ASD siblings were examined. An apparent dose-response effect was observed between autism severity and increased urinary coproporphyrins. Patients with non-chelated autism (2.25-fold, 83% had levels > 2 SD above the control mean) and non-chelated ASDs (2-fold, 58% had levels > 2 SD above the control mean), but not patients with non-chelated pervasive developmental delay-not otherwise specified (PDD-NOS) or Asperger's disorder (1.4-fold, 46% had levels > 2 SD above the control mean), had significantly increased median coproporphyrin levels versus controls. A significant increase (1.7-fold) in median coproporphyrin levels was observed among non-chelated ASD patients versus chelated ASD patients. Porphyrins should be routinely clinically measured in ASDs, and potential ASD treatments should consider monitoring porphyrin levels. Additional research should be conducted to evaluate the potential role for mercury exposure in some ASDs.

Rh and ABO maternal-fetal incompatibility and risk of autism

We hypothesized that maternal-fetal incompatibility at the Rh or ABO loci may contribute to the risk of autism. There are biologically plausible reasons to believe such effects may play a role, and two previous epidemiologic studies have provided suggestive evidence. To further test this hypothesis, we genotyped the Rh and ABO loci in a sample of 389 independent case-parent trios from the AGRE repository and analyzed the data using a modification of the log-linear model for case-parent trios in which the effects of maternal-fetal genotype incompatibility are modeled jointly with the effects of the affected child's or mother's genotypes. We did not find any evidence that incompatibility at the Rh or ABO loci increases the risk of autism. Furthermore, we did not find any evidence for the presence of a high-risk susceptibility allele at or near these two loci operating either through the mother or child.

An evaluation of the effects of thimerosal on neurodevelopmental disorders reported following DTP and Hib vaccines in comparison to DTPH vaccine in the United States

Thimerosal is an ethylmercury (49.55% mercury by weight) preservative historically added to some vaccines. Toxicokinetic studies showed children in the United States received doses of mercury from Thimerosal-containing vaccines (TCVs) in excess of safety guidelines. In the United States during the 1990s, diphtheria-tetanus-pertussis (DTP) and Haemophilus influenzae type b (Hib) vaccines (maximally, 50 mug mercury per joint administration) and diphtheria-tetanus-pertussis-Haemophilus influenzae type b (DTPH) vaccines (25 mug mercury per administration) were given to children in the same childhood vaccination schedule at 2, 4, 6, and 15-18 mo, so that children receiving DTP and Hib vaccines may have maximally received an additional 100 mug more mercury exposure from TCVs than children administered DTPH vaccines. A case-control epidemiological study of neurodevelopmental disorders (NDs) reported to the Vaccine Adverse Event Reporting System (VAERS) (online public access version; updated 31 August 2004) following administration of DTP vaccines in comparison DTPH vaccines manufactured by Lederle Laboratories (Pearl River, NY) from 1994 through 1998 was undertaken. Significantly increased odds ratios for autism, speech disorders, mental retardation, infantile spasms, and thinking abnormalities reported to VAERS were found following DTP vaccines in comparison to DTPH vaccines with minimal bias or systematic error. Additional ND research should be undertaken in the context of evaluating mercury-associated exposures, especially since in 2005 the Institute of Medicine issued a report calling into question handling of vaccine safety data by the National Immunization Program of the Centers for Disease Control and Prevention.

When science is not enough – a risk/benefit profile of thiomersal-containing vaccines

Without a preservative, such as thiomersal (known as thimerosal in the US), multi-dose liquid presentations of vaccine are vulnerable to bacteriological contamination that can result in death or serious illness of the recipient. Concerns about levels of mercury exposure from thiomersal-containing vaccines were first raised in the US during 1999 in the context of Hepatitis B vaccine for newborns. Since then, a large body of evidence from animal and epidemiological studies has accumulated on the safety of thiomersal. Ironically, these data have become largely irrelevant in wealthy countries, where mono-dose, thiomersal-free vaccines have been introduced as a precautionary measure in almost all childhood vaccines, in part related to residual public scepticism. In poor countries, multi-dose vials remain important for vaccine delivery. There is a real danger that this controversy may result in the loss to the world of thiomersal as a preservative, simply from popular pressure. In reality, it would be impossible to cease overnight using thiomersal and maintain the supply of vital vaccines. This paper reviews and summarises the data available from published studies on mercury toxicity, and thiomersal in vaccines in particular, that overwhelmingly indicate continued use of thiomersal is safe in those countries where it is most needed.

Comparison of blood and brain mercury levels in infant monkeys exposed to methylmercury or vaccines containing thimerosal

Thimerosal is a preservative that has been used in manufacturing vaccines since the 1930s. Reports have indicated that infants can receive ethylmercury (in the form of thimerosal) at or above the U.S. Environmental Protection Agency guidelines for methylmercury exposure, depending on the exact vaccinations, schedule, and size of the infant. In this study we compared the systemic disposition and brain distribution of total and inorganic mercury in infant monkeys after thimerosal exposure with those exposed to MeHg. Monkeys were exposed to MeHg (via oral gavage) or vaccines containing thimerosal (via intramuscular injection) at birth and 1, 2, and 3 weeks of age. Total blood Hg levels were determined 2, 4, and 7 days after each exposure. Total and inorganic brain Hg levels were assessed 2, 4, 7, or 28 days after the last exposure. The initial and terminal half-life of Hg in blood after thimerosal exposure was 2.1 and 8.6 days, respectively, which are significantly shorter than the elimination half-life of Hg after MeHg exposure at 21.5 days. Brain concentrations of total Hg were significantly lower by approximately 3-fold for the thimerosal-exposed monkeys when compared with the MeHg infants, whereas the average brain-to-blood concentration ratio was slightly higher for the thimerosal-exposed monkeys (3.5 +/- 0.5 vs. 2.5 +/- 0.3). A higher percentage of the total Hg in the brain was in the form of inorganic Hg for the thimerosal-exposed monkeys (34% vs. 7%). The results indicate that MeHg is not a suitable reference for risk assessment from exposure to thimerosal-derived Hg. Knowledge of the toxicokinetics and developmental toxicity of thimerosal is needed to afford a meaningful assessment of the developmental effects of thimerosal-containing vaccines.

The potential importance of steroids in the treatment of autistic spectrum disorders and other disorders involving mercury toxicity

Autism is a neurodevelopmental disorder that according to the Centers for Disease Control and Prevention (CDC) affects 1 in 150 children in the United States. Autism is characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movements, and sensory dysfunction. Recently emerging evidence suggests that mercury, especially from childhood vaccines, appears to be a factor in the development of the autistic disorders, and that autistic children have higher than normal body-burdens of mercury. In considering mercury toxicity, it has previously been shown that testosterone significantly potentates mercury toxicity, whereas estrogen is protective. Examination of autistic children has shown that the severity of autistic disorders correlates with the amount of testosterone present in the amniotic fluid, and an examination of a case-series of autistic children has shown that some have plasma testosterone levels that were significantly elevated in comparison neurotypical control children. A review of some of the current biomedical therapies for autistics, such as glutathione and cysteine, chelation, secretin, and growth hormone, suggests that they may in fact lower testosterone levels. We put forward the medical hypothesis that autistic disorders, in fact, represents a form of testosterone mercury toxicity, and based upon this observation, one can design novel treatments for autistics directed towards higher testosterone levels in autistic children. We suggest a series of experiments that need to be conducted in order to evaluate the exact mechanisms for mercury-testosterone toxicity, and various types of clinical manipulations that may be employed to control testosterone levels. It is hoped by devising therapies that address the steroid hormone pathways, in addition to the current treatments that successful lower heavy metal body-burdens of mercury, will work synergistically to improve clinical outcomes. In light of the fact that there are a number of other diseases that may have a chronic mercury toxicity component, such as Alzheimer's disease, heart disease, obesity, ALS, asthma, and other various forms of autoimmune disorders, it is imperative that further research should be conducted to understand mercury-testosterone toxicity.

Mercury in the environment: effect on health and reproduction

Mercury is a heavy metal that is found naturally in the environment in various forms. Human activity can release mercury into the air, water, and soil. Mercury is also released into the environment after its conversion to methylmercury by bacteria. Mercury was once used in medicine, but the medicinal aspect changed because of its devastating poisoning effect on humans and animals. Today, mercury is one of the most potent neurotoxins known, having a number of adverse health effects in animals and humans. As the sources of mercury are many, the general population is exposed to mercury in day-to-day life, in occupational settings, and in cases of accidental exposure. In addition, ignorance about the use of mercury in cosmetics and religious materials has opened an additional source of exposure. Therefore, making people aware of mercury's effects on health, its sources of entry into the environment, and its chelating remedies becomes a necessity so that strategies can be adopted to minimize use and exposure.