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10 mai 2011 2 10 /05 /mai /2011 17:12

Arsenic dans l'eau des puits, un poison pour le cœur

 

 

L'arsenic est le plus célèbre des poisons et les amateurs d'Agatha Christie le savent bien.

Il s'agit pourtant d'un constituant naturel de la croûte terrestre et des millions de personnes, dont au moins 13 millions aux Etats-Unis, boivent de l'eau contenant des quantités plus ou moins grandes d'arsenic. L'Agence Internationale de Recherche sur le Cancer l'a classé dans le groupe I des carcinogènes humains, mais ses effets indésirables sur la santé ne se limitent pas au cancer. Il pourrait, entre autres, avoir aussi des effets cardiovasculaires.

Une étude prospective de cohorte a été menée sur les habitants d'Araihazar, au Bengladesh.

La contamination de l'eau par l'arsenic est en effet un problème de santé publique dans ce pays, et 57 millions de personnes seraient exposées en permanence à des taux supérieurs à ceux considérés comme « standard » par l'OMS (Organisation Mondiale de la Santé).

Les concentrations de l'eau en arsenic vont dans cette région de 0,1 mug/l à 864 mug/l, offrant une variété d'exposition intéressante pour les études sinon pour les habitants eux-mêmes.

Au total 11 746 personnes se sont prêtées à l'étude, donnant leurs urines à analyser à intervalles réguliers pendant environ 6,5 ans.

Des échantillons de l'eau des puits étaient analysés en parallèle. Pendant la durée de l'étude, 198 personnes sont décédées de cause cardiovasculaire, comptant pour 43 % de la mortalité totale dans le groupe étudié.

Les auteurs estiment que 28,9 % de ces décès peuvent être attribuables à une concentration d'arsenic dans l'eau supérieure à 12 mug/l. Un effet-dose est observé entre la concentration en arsenic de l'eau et le risque de mortalité par cardiopathie ischémique ou autre pathologie cardiaque, avec, après ajustement pour les facteurs confondants, un risque presque doublé pour les concentrations les plus élevées comprises entre 148,1 et 864,0 mug/l.

Les auteurs relèvent un effet de synergie avec le tabac qui augmente la toxicité de l'arsenic. Comme dans des travaux précédents réalisés au Chili, à Taïwan et en Espagne, il n'est pas retrouvé dans cette étude de lien entre la concentration en arsenic de l'eau des puits et la mortalité cérébrovasculaire.

 

Les mécanismes liant l'arsenic aux pathologies cardiovasculaires ne sont pas encore expliqués.

Les études animales suggèrent que l'arsenic serait à l'origine d'athérosclérose, peut-être par l'intermédiaire du stress oxydatif.

 

 

Dr Roseline Péluchon

 

 

 

Chen Y et coll. : Arsenic exposure from drinking water and mortality from cardiovascular disease in Bangladesh: prospective cohort study BMJ 2011;342:d2431

 

 

BMJ. 2011 May 5;342:d2431. doi: 10.1136/bmj.d2431.

Arsenic exposure from drinking water and mortality from cardiovascular disease in Bangladesh: prospective cohort study.

Chen Y, Graziano JH, Parvez F, Liu M, Slavkovich V, Kalra T, Argos M, Islam T, Ahmed A, Rakibuz-Zaman M, Hasan R, Sarwar G, Levy D, van Geen A, Ahsan H.

Source

Department of Environmental Medicine, New York University School of Medicine, New York, NY 10016, USA.


OBJECTIVE:

To evaluate the association between arsenic exposure and mortality from cardiovascular disease and to assess whether cigarette smoking influences the association.

DESIGN:

Prospective cohort study with arsenic exposure measured in drinking water from wells and urine.

SETTING:

General population in Araihazar, Bangladesh.

PARTICIPANTS:

11746 men and women who provided urine samples in 2000 and were followed up for an average of 6.6 years.

MAIN OUTCOME MEASURE:

Death from cardiovascular disease.

RESULTS:

198 people died from diseases of circulatory system, accounting for 43% of total mortality in the population. The mortality rate for cardiovascular disease was 214.3 per 100000 person years in people drinking water containing <12.0 µg/L arsenic, compared with 271.1 per 100000 person years in people drinking water with ≥12.0 µg/L arsenic. There was a dose-response relation between exposure to arsenic in well water assessed at baseline and mortality from ischaemic heart disease and other heart disease; the hazard ratios in increasing quarters of arsenic concentration in well water (0.1-12.0, 12.1-62.0, 62.1-148.0, and 148.1-864.0 µg/L) were 1.00 (reference), 1.22 (0.65 to 2.32), 1.35 (0.71 to 2.57), and 1.92 (1.07 to 3.43) (P=0.0019 for trend), respectively, after adjustment for potential confounders including age, sex, smoking status, educational attainment, body mass index (BMI), and changes in urinary arsenic concentration since baseline. Similar associations were observed when baseline total urinary arsenic was used as the exposure variable and for mortality from ischaemic heart disease specifically. The data indicate a significant synergistic interaction between arsenic exposure and cigarette smoking in mortality from ischaemic heart disease and other heart disease. In particular, the hazard ratio for the joint effect of a moderate level of arsenic exposure (middle third of well arsenic concentration 25.3-114.0 µg/L, mean 63.5 µg/L) and cigarette smoking on mortality from heart disease was greater than the sum of the hazard ratios associated with their individual effect (relative excess risk for interaction 1.56, 0.05 to 3.14; P=0.010).

CONCLUSIONS:

Exposure to arsenic in drinking water is adversely associated with mortality from heart disease, especially among smokers.

 

Chem Biol Interact. 2011 Apr 22. [Epub ahead of print]

Physical setting and natural sources of exposure to carcinogenic trace elements and radionuclides in Lahontan Valley, Nevada.

Seiler R.

Source

US Geological Survey, 2730 N. Deer Run Road, Carson City, NV 89701, USA.

 

In Lahontan Valley, Nevada, arsenic, cobalt, tungsten, uranium, radon, and polonium-210 are carcinogens that occur naturally in sediments and groundwater.

Arsenic and cobalt are principally derived from erosion of volcanic rocks in the local mountains and tungsten and uranium are derived from erosion of granitic rocks in headwater reaches of the Carson River.

Radon and (210)Po originate from radioactive decay of uranium in the sediments. Arsenic, aluminum, cobalt, iron, and manganese concentrations in household dust suggest it is derived from the local soils.

Excess zinc and chromium in the dust are probably derived from the vacuum cleaner used to collect the dust, or household sources such as the furnace. Some samples have more than 5 times more cobalt in the dust than in the local soil, but whether the source of the excess cobalt is anthropogenic or natural cannot be determined with the available data. Cobalt concentrations are low in groundwater, but arsenic, uranium, radon, and (210)Po concentrations often exceed human-health standards, and sometime greatly exceed them.

Exposure to radon and its decay products in drinking water can vary significantly depending on when during the day that the water is consumed. Although the data suggests there have been no long term changes in groundwater chemistry that corresponds to the Lahontan Valley leukemia cluster, the occurrence of the very unusual leukemia cluster in an area with numerous (210)Po and arsenic contaminated wells is striking, particularly in conjunction with the exceptionally high levels of urinary tungsten in Lahontan Valley residents.

Additional research is needed on potential exposure pathways involving food or inhalation, and on synergistic effects of mixtures of these natural contaminants on susceptibility to development of leukemia.


 

PMID: 21536017 [PubMed - as supplied by publisher]

 

 

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