http://autism.com/triggers/vaccine/mercury.htm
Autism: a Novel Form of Mercury Poisoning
S. Bernard, B.A., A. Enayati, M.S.M.E., L. Redwood, M.S.N., H. Roger, B.A., T. Binstock
Sallie Bernard, ARC Research, 14 Commerce Drive, Cranford, NJ 07901 USA, 908.276.6300, fax 908.276.1301
Summary Autism is a syndrome characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movements, and sensory dysfunction. Recent epidemiological studies suggest that autism may affect 1 in 150 U. S. children. Exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism, and the similarities extend to neuroanatomy, neurotransmitters, and biochemistry. Thimerosal, a preservative added to many vaccines, has become a major source of mercury in children who, within their first two years, may have received a quantity of mercury that exceeds safety guidelines. A review of medical literature and U.S. government data suggests that (i) many cases of idiopathic autism are induced by early mercury exposure from thimerosal; (ii) this type of autism represents an unrecognized mercurial syndrome; and (iii) genetic and non-genetic factors establish a predisposition whereby thimerosal's adverse effects occur only in some children.
INTRODUCTION
Autistic Spectrum Disorder (ASD) is a neurodevelopmental syndrome with onset prior to age 36 months. Diagnostic criteria consist of impairments in sociality and communication plus repetitive and stereotypic behaviors (1). Traits strongly associated with autism include movement disorders and sensory dysfunctions (2). Although autism may be apparent soon after birth, most autistic children experience at least several months, even a year or more of normal development -- followed by regression, defined as loss of function or failure to progress (2,3,4).
The neurotoxicity of mercury (Hg) has long been recognized (5). Primary data derive from victims of contaminated fish (Japan - Minamata Disease) or grain (Iraq, Guatemala, Russia); from acrodynia (Pink Disease) induced by Hg in teething powders; and from individual instances of mercury poisoning (HgP), many occurring in occupational settings (e.g., Mad Hatter's Disease). Animal and in vitro studies also provide insights into the mechanisms of Hg toxicity. More recently, the Food and Drug Administration (FDA) and the American Academy of Pediatrics (AAP) have determined that the typical amount of Hg injected into infants and toddlers via childhood immunizations has exceeded government safety guidelines on an individual (6) and cumulative vaccine basis (7). The mercury in vaccines derives from thimerosal (TMS), a preservative which is 49.6% ethylmercury (eHg) (7).
Past cases of HgP have presented with much inter-individual variation, depending on the dose, type of mercury, method of administration, duration of exposure, and individual sensitivity. Thus, while commonalities exist across the various instances of HgP, each set of variables has given rise to a different disease manifestation (8,9,10,11). It is hypothesized that the regressive form of autism represents another form of mercury poisoning, based on a thorough correspondence between autistic and HgP traits and physiological abnormalities, as well as on the known exposure to mercury through vaccines. Furthermore, other phenomena are consistent with a causal Hg-ASD relationship. These include (a) symptom onset shortly after immunization; (b) ASD prevalence increases corresponding to vaccination increases; (c) similar sex ratios of affected individuals; (d) a high heritability rate for autism paralleling a genetic predisposition to Hg sensitivity at low doses; and (e) parental reports of autistic children with elevated Hg.
Trait Comparison
ASD manifests a constellation of symptoms with much inter-individual variation (3,4). A comparison of traits defining, nearly universal to, or commonly found in autism with those known to arise from mercury poisoning is given in Table I. The characteristics defining or strongly associated with autism are also more fully described.
Autism has been conceived primarily as a psychiatric condition; and two of its three diagnostic criteria are based upon the observable traits of (a) impairments in sociality, most commonly social withdrawal or aloofness, and (b) a variety of perseverative or stereotypic behaviors and the need for sameness, which strongly resemble obsessive-compulsive tendencies. Differential diagnosis may include childhood schizophrenia, depression, obsessive-compulsive disorder (OCD), anxiety disorder, and other neuroses. Related behaviors commonly found in ASD individuals are irrational fears, poor eye contact, aggressive behaviors, temper tantrums, irritability, and inexplicable changes in mood (1,2,12-17). Mercury poisoning, when undetected, is often initially diagnosed as a psychiatric disorder (18). Commonly occurring symptoms include (a) "extreme shyness," indifference to others, active avoidance of others, or “a desire to be alone”; (b) depression, “lack of interest” and “mental confusion;” (c) irritability, aggression, and tantrums in children and adults; (d) anxiety and fearfulness; and (e) emotional lability. Neuroses, including schizoid and obsessive-compulsive traits, problems in inhibition of perseveration, and stereotyped behaviors, have been reported in a number of cases; and lack of eye contact was observed in one 12 year old girl with mercury vapor poisoning (18-35).
The third diagnostic criterion for ASD is impairment in communication (1). Historically, about half of those with classic autism failed to develop meaningful speech (2), and articulation difficulties are common (3). Higher functioning individuals may have language fluency but still show semantic and pragmatic errors (3,36). In many cases of ASD, verbal IQ is lower than performance IQ (3). Similarly, mercury-exposed children and adults show a marked difficulty with speech (9,19,37). In milder cases scores on language tests may be lower than those of unexposed controls (31,38). Iraqi children who were postnatally poisoned developed articulation problems, from slow, slurred word production to an inability to generate meaningful speech; while Iraqi babies exposed prenatally either failed to develop language or presented with severe language deficits in childhood (23,24,39). Workers with Mad Hatter's disease had word retrieval and articulation difficulties (21).
Nearly all cases of ASD and HgP involve disorders of physical movement (2,30,40). Clumsiness or lack of coordination has been described in many higher functioning ASD individuals (41). Infants and toddlers later diagnosed with autism may fail to crawl properly or may fall over while sitting or standing; and the movement disturbances typically occur on the right side of the body (42). Problems with intentional movement and imitation are common in ASD, as are a variety of unusual stereotypic behaviors such as toe walking, rocking, abnormal postures, choreiform movements, spinning; and hand flapping (2,3,43,44). Noteworthy because of similarities to autism are reports in Hg literature of (a) children in Iraq and Japan who were unable to stand, sit, or crawl (34,39); (b) Minamata disease patients whose movement disturbances were localized to one side of the body, and a girl exposed to Hg vapor who tended to fall to the right (18,34); (c) flapping motions in an infant poisoned from contaminated pork (37) and in a man injected with thimerosal (27); (d) choreiform movements in mercury vapor intoxication (19); (e) toe walking in a moderately poisoned Minamata child (34); (f) poor coordination and clumsiness among victims of acrodynia (45); (g) rocking among infants with acrodynia (11); and (h) unusual postures observed in both acrodynia and mercury vapor poisoning (11,31). The presence of flapping motions in both diseases is of interest because it is such an unusual behavior that it has been recommended as a diagnostic marker for autism (46).
Virtually all ASD subjects show a variety of sensory abnormalities (2). Auditory deficits are present in a minority of individuals and can range from mild to profound hearing loss (2,47). Over- or under-reaction to sound is nearly universal (2,48), and deficits in language comprehension are often present (3). Pain sensitivity or insensitivity is common, as is a general aversion to touch; abnormal sensation in the extremities and mouth may also be present and has been detected even in toddlers under 12 months old (2,49). There may be a variety of visual disturbances, including sensitivity to light (2,50,51,52). As in autism, sensory issues are reported in virtually all instances of Hg toxicity (40). HgP can lead to mild to profound hearing loss (40); speech discrimination is especially impaired (9,34,). Iraqi babies exposed prenatally showed exaggerated reaction to noise (23), while in acrodynia, patients reported noise sensitivity (45). Abnormal sensation in the extremities and mouth is the most common sensory disturbance (25,28). Acrodynia sufferers and prenatally exposed Iraqi babies exhibited excessive pain when bumping limbs and an aversion to touch (23,24,45,53). A range of visual problems has been reported, including photophobia (18,23,34).
Comparison of Biological Abnormalities
The biological abnormalities commonly found in autism are listed in Table II, along with the corresponding pathologies arising from mercury exposure. Especially noteworthy similarities are described.
Autism is a neurodevelopmental disorder which has been characterized as "a disorder of neuronal organization, that is, the development of the dentritic tree, synaptogenesis, and the development of the complex connectivity within and between brain regions" (54). Depressed expression of neural cell adhesion molecules (NCAMs), which are critical during brain development for proper synaptic structuring, has been found in one study of autism (55). Organic mercury, which readily crosses the blood-brain barrier, preferentially targets nerve cells and nerve fibers (56); primates accumulate the highest Hg-levels in the brain relative to other organs (40). Furthermore, although most cells respond to mercurial injury by modulating levels of glutathione (GSH), metallothionein, hemoxygenase, and other stress proteins, neurons tend to be “markedly deficient in these responses” and thus are less able to remove Hg and more prone to Hg-induced injury (56). In the developing brain, mercury interferes with neuronal migration, depresses cell division, disrupts microtubule function, and reduces NCAMs (28, 57-59).
While damage has been observed in a number of brain areas in autism, many nuclei and functions are spared (36). HgP’s damage is similarly selective (40). Numerous studies link autism with neuronal atypicalities within the amygdala, hippocampi, basal ganglia, the Purkinje and granule cells of the cerebellum, brainstem, basal ganglia, and cerebral cortex (36,60-69). Each of these areas can be affected by HgP (10,34,40,70-73). Migration of Hg, including eHg, into the amygdala is particularly noteworthy, because in primates this brain region has neurons specific for eye contact (74) and it is implicated in autism and in social behaviors (65,66,75).
Autistic brains show neurotransmitter irregularities which are virtually identical to those arising from Hg exposure: both high or low serotonin and dopamine, depending on the subjects studied; elevated epinephrine and norepinephrine in plasma and brain; elevated glutamate; and acetylcholine deficiency in hippocampus (2,21,76-83).
Gillberg and Coleman (2) estimate that 35-45% of autistics eventually develop epilepsy. A recent MEG study reported epileptiform activity in 82% of 50 regressive autistic children; in another study, half the autistic children expressed abnormal EEG activity during sleep (84). Autistic EEG abnormalities tend to be non-specific and have a variety of patterns (85). Unusual epileptiform activity has been found in a number of mercury poisoning cases (18,27,34,86-88). Early mHg exposure enhances tendencies toward epileptiform activity with a reduced level of seizure-discharge amplitude (89), a finding consistent with the subtlety of seizures in many autism spectrum children (84,85). The fact that Hg increases extracellular glutamate would also contribute to epileptiform activity (90).
Some autistic children show a low capacity to oxidize sulfur compounds and low levels of sulfate (91,92). These findings may be linked with HgP because (a) Hg preferentially binds to sulfhydryl molecules (-SH) such as cysteine and GSH, thereby impairing various cellular functions (40), and (b) mercury can irreversibly block the sulfate transporter NaSi cotransporter NaSi-1, present in kidneys and intestines, thus reducing sulfate absorption (93). Besides low sulfate, many autistics have low GSH levels, abnormal GSH-peroxidase activity within erythrocytes, and decreased hepatic ability to detoxify xenobiotics (91,94,95). GSH participates in cellular detoxification of heavy metals (96); hepatic GSH is a primary substrate for organic-Hg clearance from the human (40); and intraneuronal GSH participates in various protective responses against Hg in the CNS (56). By preferentially binding with GSH, preventing absorption of sulfate, or inhibiting the enzymes of glutathione metabolism (97), Hg might diminish GSH bioavailability. Low GSH can also derive from chronic infection (98,99), which would be more likely in the presence of immune impairments arising from mercury (100). Furthermore, mercury disrupts purine and pyrimidine metabolism (97,10). Altered purine or pyrimidine metabolism can induce autistic features and classical autism (2,101,102), suggesting another mechanism by which Hg can contribute to autistic traits.
Autistics are more likely to have allergies, asthma, selective IgA deficiency (sIgAd), enhanced expression of HLA-DR antigen, and an absence of interleukin-2 receptors, as well as familial autoimmunity and a variety of autoimmune phenomena. These include elevated serum IgG and ANA titers, IgM and IgG brain antibodies, and myelin basic protein (MBP) antibodies (103-110). Similarly, atypical responses to Hg have been ascribed to allergic or autoimmune reactions (8), and genetic predisposition to such reactions may explain why Hg sensitivity varies so widely by individual (88,111). Children who developed acrodynia were more likely to have asthma and other allergies (11); IgG brain autoantibodies, MBP, and ANA have been found in HgP subjects (18,111,112); and mice genetically prone to develop autoimmune diseases "are highly susceptible to mercury-induced immunopathological alterations" even at the lowest doses (113). Additionally, many autistics have reduced natural killer cell (NK) function, as well as immune-cell subsets shifted in a Th2 direction and increased urine neopterin levels, indicating immune system activiation (103,114-116). Depending upon genetic predisposition, Hg can induce immune activation, an expansion of Th2 subsets, and decreased NK activity (117-120).
Population Characteristics
In most affected children, autistic symptoms emerge gradually, although there are cases of sudden onset (3). The earliest abnormalities have been detected in 4 month olds and consist of subtle movement disturbances; subtle motor-sensory disturbances have been observed in 9 month olds (49). More overt speech and hearing difficulties become noticeable to parents and pediatricians between 12 and 18 months (2). TMS vaccines have been given in repeated intervals starting from infancy and continuing until 12 to 18 months. While HgP symptoms, may arise suddenly in especially sensitive individuals (11), usually there is a preclinical "silent stage" in which subtle neurological changes are occuring (121) and then a gradual emergence of symptoms. The first symptoms are typically sensory- and motor-related, which are followed by speech and hearing deficits, and finally the full array of HgP characteristics (40). Thus, both the timing and nature of symptom emergence in ASD are fully consistent with a vaccinal Hg etiology. This parallel is reinforced by parental reports of excessive amounts of mercury in urine or hair from younger autistic children, as well as some improvement in symptoms with standard chelation therapy (122).
The discovery and rise in prevalence of ASD mirrors the introduction and spread of TMS in vaccines. Autism was first described in 1943 among children born in the 1930s (123). Thimerosal was first introduced into vaccines in the 1930s (7). In studies conducted prior to 1970, autism prevalence was estimated, at 1 in 2000; in studies from 1970 to 1990 it averaged 1 in 1000 (124). This was a period of increased vaccination rates of the TMS-containing DPT vaccines among children in the developed world. In the early 1990s, the prevalence of autism was found to be 1 in 500 (125), and in 2000 the CDC found 1 in 150 children affected in one community, which was consistent with reports from other areas in the country (126). In the late 1980s and early 1990s, two new TMS vaccines, the HIB and Hepatitis B, were added to the recommended schedule (7).
Nearly all US children are immunized, yet only a small proportion develop autism. A pertinent characteristic of mercury is the great variability in its effects by individual, so that at the same exposure level, some will be affected severely while others will be asymptomatic (9,11,28). An example is acrodynia, which arose in the early 20th Century from mercury in teething powders and afflicted only 1 in 500-1000 children given the same low dose (28). Studies in mice as well as humans indicate that susceptibility to Hg effects arises from genetic status, in some cases including a propensity to autoimmune disorders (113,34,40). ASD exhibits a strong genetic component, with high concordance in monozygotic twins and a higher than expected incidence among siblings (4); autism is also more prevalent in families with autoimmune disorders (106).
Additionally, autism is more prevalent among boys than girls, with the ratio estimated at 4:1 (2). Mercury studies in mice and humans consistently report greater effects on males than females, except for kidney damage (57). At high doses, both sexes are affected equally; at low doses only males are affected (38,40,127).
Discussion
We have shown that every major characteristic of autism has been exhibited in at least several cases of documented mercury poisoning. Recently, the FDA and AAP have revealed that the amount of mercury given to infants from vaccinations has exceeded safety levels. The timing of mercury administration via vaccines coincides with the onset of autistic symptoms. Parental reports of autistic children with measurable mercury levels in hair and urine indicate a history of mercury exposure. Thus the standard primary criteria for a diagnosis of mercury poisoning - observable symptoms, known exposure at the time of symptom onset, and detectable levels in biologic samples (11,31) - have been met in autism. As such, mercury toxicity may be a significant etiological factor in at least some cases of regressive autism. Further, each known form of HgP in the past has resulted in a unique variation of mercurialism - e.g., Minamata disease, acrodynia, Mad Hatter’s disease - none of which has been autism, suggesting that the Hg source which may be involved in ASD has not yet been characterized; given that most infants receive eHg via vaccines, and given that the effect on infants of eHg in vaccines has never been studied (129), vaccinal thimerosal should be considered a probable source. It is also possible that vaccinal eHg may be additive to a prenatal mercury load derived from maternal amalgams, immune globulin injections, or fish consumption, and environmental sources.
Conclusion
The history of acrodynia illustrates that a severe disorder, afflicting a small but significant percentage of children, can arise from a seemingly benign application of low doses of mercury. This review establishes the likelihood that Hg may likewise be etiologically significant in ASD, with the Hg derived from thimerosal in vaccines rather than teething powders. Due to the extensive parallels between autism and HgP, the likelihood of a causal relationship is great. Given this possibility, TMS should be removed from all childhood vaccines, and the mechanisms of Hg toxicity in autism should be thoroughly investigated. With perhaps 1 in 150 children now diagnosed with ASD, development of HgP-related treatments, such as chelation, would prove beneficial for this large and seemingly growing population.
