Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD, USA.
Environ Health. 2012 Feb 17;11:6. doi: 10.1186/1476-069X-11-6.
Nitrate is a widespread contaminant of drinking water supplies, especially in agricultural areas. Nitrate intake from drinking water and dietary sources can interfere with the uptake of iodide by the thyroid, thus potentially impacting thyroid function.
We assessed the relation of estimated nitrate levels in well water supplies with thyroid health in a cohort of 2,543 Old Order Amish residing in Lancaster, Chester, and Lebanon counties in Pennsylvania for whom thyroid stimulating hormone (TSH) levels were measured during 1995-2008. Nitrate measurement data (1976-2006) for 3,613 wells in the study area were obtained from the U.S. Geological Survey and we used these data to estimate concentrations at study participants' residences using a standard linear mixed effects model that included hydrogeological covariates and kriging of the wells' residuals. Nitrate levels estimated by the model ranged from 0.35 mg/L to 16.4 mg/L N-NO3(-), with a median value of 6.5 mg/L, which was used as the cutpoint to define high and low nitrate exposure. In a validation analysis of the model, we calculated that the sensitivity of the model was 67% and the specificity was 93%. TSH levels were used to define the following outcomes: clinical hyperthyroidism (n = 10), clinical hypothyroidism (n = 56), subclinical hyperthyroidism (n = 25), and subclinical hypothyroidism (n = 228).
In women, high nitrate exposure was significantly associated with subclinical hypothyroidism (OR = 1.60; 95% CI: 1.11-2.32). Nitrate was not associated with subclinical thyroid disease in men or with clinical thyroid disease in men or women.
Although these data do not provide strong support for an association between nitrate in drinking water and thyroid health, our results do suggest that further exploration of this hypothesis is warranted using studies that incorporate individual measures of both dietary and drinking water nitrate intake.
硝酸盐是饮用水供应中广泛存在的污染物，尤其是在农业地区。饮用水和饮食中硝酸盐的摄入会干扰甲状腺对碘的摄取，从而可能影响甲状腺功能。
我们评估了宾夕法尼亚州兰开斯特、切斯特和黎巴嫩县的 2543 名老秩序阿米什人群的井水估计硝酸盐水平与甲状腺健康之间的关系，这些人在 1995-2008 年期间测量了促甲状腺激素（TSH）水平。研究区域的 3613 口井的硝酸盐测量数据（1976-2006 年）来自美国地质调查局，我们使用这些数据通过标准线性混合效应模型来估计研究参与者住所的浓度，该模型包括水文地质协变量和井残差的克里金插值。模型估计的硝酸盐水平范围从 0.35 毫克/升至 16.4 毫克/升 N-NO3(-)，中位数为 6.5 毫克/升，用作定义高和低硝酸盐暴露的切点。在对模型的验证分析中，我们计算出模型的灵敏度为 67%，特异性为 93%。TSH 水平用于定义以下结果：临床甲状腺功能亢进症（n=10）、临床甲状腺功能减退症（n=56）、亚临床甲状腺功能亢进症（n=25）和亚临床甲状腺功能减退症（n=228）。
在女性中，高硝酸盐暴露与亚临床甲状腺功能减退症显著相关（OR=1.60；95%CI：1.11-2.32）。硝酸盐与男性的亚临床甲状腺疾病或男性和女性的临床甲状腺疾病均无关联。
尽管这些数据并未为饮用水中的硝酸盐与甲状腺健康之间的关联提供有力支持，但我们的结果确实表明，使用同时包含饮食和饮用水硝酸盐摄入量个体测量值的研究进一步探讨这一假设是合理的。
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