The Association of Exposure to Lead, Mercury, and Selenium and the Development of Amyotrophic Lateral Sclerosis and the Epigenetic Implications

Abstract

Metal exposures are an intriguing potential culprit in the cause of sporadic amyotrophic lateral sclerosis (ALS). For one, there are numerous case reports linking different metals to an ALS phenotype. Furthermore, some investigators have demonstrated higher levels of certain metals in the blood, bone, cerebrospinal fluid, urine, or spinal cords of patients with ALS compared to controls. There are also many case-control studies looking at the possible association of certain metals with the development of ALS. We have reviewed the relevant literature regarding metal exposures and the risk of developing ALS. We found that many different metals have been implicated as having a role in ALS, but there is more literature investigating the role of lead than any other metal. Despite many studies, the role, if any, of this metal in the pathogenesis of ALS remains unclear. Similarly, other metals either have inconclusive, conflicting, or insufficient results in order to make a definitive conclusion. One explanation for these findings is that metal exposures alone are insufficient for the development of ALS. Perhaps an interaction between the metal exposure and an individual’s genetic makeup is required to produce epigenetic changes that ultimately lead to ALS.

Risk agents related to work and amyotrophic lateral sclerosis: An occupational medicine focus

“…Some metals investigated as implicated in ALS are correlated to the mercury (Hg) and cadmium. Mercury may be implicated as a risk factor for development of the pathology [78]. Clinical ALS symptoms in patients accidentally exposed to Hg [79] have been observed in a work published by Schwarz et al [79].…”

“…Observing the conflicting evidence in the literature regarding the role of Hg in the etiology of ALS, is hoped to bring about a greater interest in this topic [84]. [78] review some evidence leads to the hypothesis that an interaction between heavy metal exposure and an individual's genetic makeup is required to produce epigenetic changes that ultimately lead to ALS DDT -dichlorodiphenyltrichloroethane; ELF-EMF -extremely low-frequency electromagnetic field; MET -metabolic equivalent. role in the gene expression control, may be involved in the complexity of the disease in its phenotypes and progression [91][92][93].…”

Controlled population-based comparative study of USA and international adult [55-74] neurological deaths 1989-2014

“…Including such factors as occupation, heavy metals, petro‐chemicals, organophosphate/pesticides26, 27, 28, 29, 30 and possible influence of electromagnetic field (EMF)18, 25, 31 and military service 32. Although not all studies related to ALS have consistently reported environmental factors,33 the majority have highlighted environmental factors rather than longevity4, 5, 6, 7, 8, 18, 25, 26, 27, 28, 29, 30 as well as epigenetic changes,33, 34, 35 whist recently, research had linked rises in dementias to proximity to major roads 30…”

Role of Predictive Variables and Their Interplay to Develop Anemia in Traffic Wardens

“…Lead, a toxic compound can induce adverse effects in each biological system by damaging hematopoietic, nervous, renal, cardiovascular, immune and reproductive system [1,2]. Engine exhaust from traffic vehicles is the primary source of toxicity of lead because it contains various toxic chemicals that are hazardous for the human body [3].…”