Amyotrophic lateral sclerosis (ALS) is a progressive and fatal degenerative disorder of motor neurons. The cause of this degeneration is unknown, and different causal hypotheses include genetic, viral, traumatic and environmental mechanisms. In this study, we have analyzed metal concentrations in cerebrospinal fluid (CSF) and blood plasma in a well-defined cohort (n = 17) of ALS patients diagnosed with quantitative electromyography. Metal analyses were performed with high-resolution inductively coupled plasma mass spectrometry. Statistically significant higher concentrations of manganese, aluminium, cadmium, cobalt, copper, zinc, lead, vanadium and uranium were found in ALS CSF compared to control CSF. We also report higher concentrations of these metals in ALS CSF than in ALS blood plasma, which indicate mechanisms of accumulation, e.g. inward directed transport. A pattern of multiple toxic metals is seen in ALS CSF. The results support the hypothesis that metals with neurotoxic effects are involved in the pathogenesis of ALS.

Metal Concentrations in Cerebrospinal Fluid and Blood Plasma from Patients with Amyotrophic Lateral Sclerosis

Objective The association between occupational exposure to lead and amyotrophic lateral sclerosis (ALS) was examined through systematic review and meta-analyses of relevant epidemiological studies and reported according to PRISMA guidelines. Methods Relevant studies were searched in multiple bibliographic databases through September 2013; additional articles were tracked through PubMed until submission. All records were screened in DistillerSR, and the data extracted from included articles were synthesized with meta-analysis. Results The risk of developing ALS among individuals with a history of exposure to lead was almost doubled (odds ratio, 1.81; 95% confidence interval, 1.39 to 2.36) on the basis of nine included case-control studies with specific lead exposure information, with no apparent heterogeneity across included studies (I = 14%). The attributable risk of ALS because of exposure to lead was estimated to be 5%. Conclusions Previous exposure to lead may be a risk factor for ALS.

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A meta-analysis of observational studies of the association between chronic occupational exposure to lead and amyotrophic lateral sclerosis

Concentrations of Pb, Cd, and other metals in tissues of 17 free-range and 32 commercial broiler chickens from the Kabwe mining town in Zambia were determined. Mean concentrations of Pb and Cd exceeded maximum levels for human consumption in some organs including muscle (Pb only) in free-range chickens, in contrast to low levels in broiler chickens. Human consumers in Kabwe could be exposed to Pb and Cd in free-range chickens. Environ. Toxicol. Chem. 2013;32:189–192. © 2012 SETAC

https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.2029

Metal distribution in tissues of free-range chickens near a lead-zinc mine in Kabwe, Zambia.

Twenty mixed-breed adult laying hens from a small farm flock in Iowa were clinically normal but had been exposed to chips of lead-based paint in their environment. These chickens were brought to the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, where the concentration of lead in blood, eggs (yolk, albumen, and shell), and tissues (liver, kidney, muscle, and ovary) from 5 selected chickens was determined over a period of 9 days. Blood lead levels ranged from less than 50 to 760 ppb. Lead contamination of the yolks varied from less than 20 to 400 ppb, and shells were found to contain up to 450 ppb lead. Albumen contained no detectable amount. Lead content of the egg yolks strongly correlated with blood lead levels. Deposition of lead in the shells did not correlate well with blood lead levels. Mean tissue lead accumulation was highest in kidneys (1,360 ppb), with livers ranking second (500 ppb) and ovarian tissue third (320 ppb). Muscle contained the lowest level of lead (280 ppb). Lead contamination of egg yolks and edible chicken tissues represents a potential public health hazard, especially to children repeatedly consuming eggs from contaminated family-owned flocks.

https://vdi.sagepub.com/content/15/5/418.full.pdf

Lead contamination of chicken eggs and tissues from a small farm flock.

SUMMARY. In a study of chronic lead intoxication in mature chickens, blood lead levels were significantly lower in hens than in roosters receiving the same oral dose of lead. It was then shown that eggshells from lead-treated hens contained 6-12 times the lead concentration of eggshells from control hens. Similarly, the lead content of egg yolks from treated hens was significantly higher than yolks from controls. Lead-treated hens laid significantly more eggs during the period of observation of nearly 3 years because of the increased frequency of laying cycles, which was almost three times that of control hens. A further observation was histologic damage to the mature testes of the rooster. RESUMEN. Efecto de la intoxicaci6n cr6nica por plomo en aves adultas. En un modelo para la intoxicaci6n cronica por plomo en aves adultas, se encontr6 que los niveles sanguineos de plomo fueron significantemente menores en gallinas que en gallos que recibieron la misma dosis oral de plomo. Subsecuentemente se demostro que las cascaras de los huevos procedentes de las gallinas tratadas con plomo contenian de 6 a 12 veces la concentraci6n encontrada en los huevos de las aves controles. Asi mismo, el contenido de plomo en las yemas de los huevos de las gallinas tratadas fue significantemente mayor que en los controles. Las gallinas tratadas con plomo pusieron un numero significantemente mayor de huevos durante el periodo de observaci6n de casi tres afios debido al aumento en la frecuencia de los ciclos de postura que fue casi tres veces que el de las gallinas controles. Una observaci6n adicional fue el daiio histol6gico en los testiculos de los gallos adultos.

Michel Silbermann

Papers

The effects of long-term lead intoxication on the nervous system of the chicken.