A new study published in Environmental Research by a group of researchers in upstate New York underscores this point. Lead author Dr. Brooks Gump of Syracuse University and coauthors call attention to problems associated with low levels of background exposure to lead and mercury, at concentrations notably lower than those deemed "elevated" by federal agencies such as the Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA).
The authors report on results from the Environmental Exposures and Child Health Outcomes (EECHO) study, an ongoing study involving African-American and white children (ages 9-11) in low- and middle-income urban neighborhoods. Although the EECHO study's primary purpose is to investigate the influence of environmental toxicant exposures on cardiovascular risk indices, the Environmental Research paper focuses on interesting associations between environmental toxicants and neurodevelopmental outcomes.
Study Description
The sample included 203 children (53% male, 57% African-American). Over half (53%) of the families had incomes of less than $35,000 per year. The study measured:
- Blood levels of lead and total mercury
- Hostility (administered to participants)
- Other disruptive behaviors (administered to parents), including oppositional defiant disorder (ODD) behaviors and attention-deficit/hyperactivity disorder (ADHD) behaviors
- Emotion regulation (participants)
- Autism spectrum disorder (ASD) symptoms (parents)
The investigators found significant associations with hostile distrust, ODD behaviors, lack of emotional awareness, and emotional uncertainty correlating with increasing blood lead levels. These significant associations occurred in children with blood lead levels (0.19 to 3.25 micrograms per deciliter) well below the reference level of 5 micrograms per deciliter at which the CDC recommends initiating public health actions.
Gump and coauthors also measured heart rate variability (HRV) to assess parasympathetic (vagal) responses to acute stress. They explain that they included HRV because emerging research suggests that underlying differences in parasympathetic nervous system responses to acute stress may shape neurobiological susceptibility to environmental factors. After Gump's research team added HRV measures to their statistical models as interaction terms, they found a statistically significant and "novel" relationship between blood mercury levels and ASD symptoms (especially social skills, attention to detail, and imagination) in the subgroup of children who showed sustained vagal tone during acute stress. This latter result matches findings from a 2003 study in which autistic children displayed an "excessively controlled vagal system" suggestive of "autonomic hyperarousal." The authors point to the need for further research to elaborate on mercury's role in triggering greater frequency of autism spectrum symptoms in children who exhibit atypical parasympathetic activity.
Comments
In a separate publication about the EECHO study, the authors explicitly note their assumption that "the majority of total mercury in whole blood was methylmercury via fish consumption," adding that they did not carry out mercury speciation to verify their assumption. This is a notable limitation of the study, because measurement of blood levels of heavy metals assesses recent (or ongoing) exposure to heavy metals but is not an accurate method of determining whether the organs, tissues, or bones are storing these toxicants. Many US children still receive thimerosal-containing flu shots on an annual basis; these contain significant amounts of ethylmercury, which moves more quickly into tissues and organs than methylmercury.
The authors point to the need for further research to elaborate on mercury's role in triggering "greater frequency of autism spectrum symptoms" in children who exhibit atypical parasympathetic activity.
Despite this oversight, the authors emphasize the importance of paying attention to low levels of background metal exposure because "background exposures...affect a much larger proportion of children." This comment calls into question the relevance of "safety" thresholds for highly toxic substances. Just as Ralph Nadar once warned that some cars were "unsafe at any speed," it seems clear that toxicants such as lead and mercury are unsafe at any level.
Here's a presentation on the site of the Int'l Academy of Oral Medicine & Toxicology, IAOMT, that simply nails the facts [Link] . Note the name 'Dr. Murray Vimy' in the credits to many of the papers referenced.
Here he is on YouTube discussing the Canadian gov't's ridiculous flip-flopping on the issue, this despite it costing Canadian taxpayers hundreds of millions every year to mop up after the damage done by these so-called 'enomomical fillings', to quote the morons at the Canadian Dental Association.