Consumption of water contaminated by nitrate and its deleterious effects on the human thyroid gland: a review and update

García-Torres, Edgar; Morales, R. Pérez; González‐Zamora, Alberto; Ríos-Sánchez, Efraín; Calderón, Edgar Héctor Olivas; Romero, José de Jesús Alba; Rincón, Esperanza Yasmín Calleros

doi:10.1080/09603123.2020.1815664

Cited by 25 publications

(9 citation statements)

References 107 publications

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“…However, due to excessive use of fertilizers, septic systems in rural areas, food processing waste and industrial waste, nitrate levels in the food and water can increase. Nitrate ion competitively binds to NIS, resulting in low iodine intake in the thyroid gland (reviewed in [ 439 ]). Higher exposure to nitrate has even been associated with a higher risk of developing hypothyroidism [ 440 , 441 ].…”

Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

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Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene–environment interactions underlying the pathology of thyroid diseases.

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Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

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“…Nitrates, although produced naturally, have carcinogenic properties due to the endogenous formation of N-nitroso compounds. They can act as EDCs as they are NIS inhibitors, inhibit TPO and thyroglobulin (Tg, thyroid glycoprotein required for thyroid hormone synthesis), and generate reactive oxygen species (ROS); consumption of water contaminated with nitrates may affect thyroid function in humans [39].…”

Section: Thyroid Disruptors-general Informationmentioning

confidence: 99%

Iodine as a potential endocrine disruptor—a role of oxidative stress

et al. 2022

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Purpose Iodine is an essential micronutrient required for thyroid hormone biosynthesis. However, overtreatment with iodine can unfavorably affect thyroid physiology. The aim of this review is to present the evidence that iodine—when in excess—can interfere with thyroid hormone synthesis and, therefore, can act as a potential endocrine-disrupting chemical (EDC), and that this action, as well as other abnormalities in the thyroid, occurs—at least partially—via oxidative stress. Methods We reviewed published studies on iodine as a potential EDC, with particular emphasis on the phenomenon of oxidative stress. Results This paper summarizes current knowledge on iodine excess in the context of its properties as an EDC and its effects on oxidative processes. Conclusion Iodine does fulfill the criteria of an EDC because it is an exogenous chemical that interferes—when in excess—with thyroid hormone synthesis. However, this statement cannot change general rules regarding iodine supply, which means that iodine deficiency should be still eliminated worldwide and, at the same time, iodine excess should be avoided. Universal awareness that iodine is a potential EDC would make consumers more careful regarding their diet and what they supplement in tablets, and—what is of great importance—it would make caregivers choose iodine-containing medications (or other chemicals) more prudently. It should be stressed that compared to iodine deficiency, iodine in excess (acting either as a potential EDC or via other mechanisms) is much less harmful in such a sense that it affects only a small percentage of sensitive individuals, whereas the former affects whole populations; therefore, it causes endemic consequences.

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“…12 At this time, the strongest evidence supports associations between drinking water nitrate intake and infant methemoglobinemia, thyroid disease, neural tube defects, and colorectal cancer, though other associations have been reported. 1,13 The EPA drinking water maximum contaminant level (MCL) for nitrate (10 mg/L NO 3 -N) was set to protect against infant methemoglobinemia, an acute condition, 14 but other adverse health effects have been observed at exposure below this level. 1…”

Section: Introductionmentioning

confidence: 99%

Drinking water sources and water quality in a prospective agricultural cohort

Manley

Spaur

Madrigal

et al. 2022

Environmental Epidemiology

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We describe drinking water sources and water quality for a large agricultural cohort. We used questionnaire data from the Agricultural Health Study (N = 89,655), a cohort of licensed pesticide applicators and their spouses in Iowa (IA) and North Carolina (NC), to ascertain drinking water source at enrollment (1993–1997). For users of public water supplies (PWS), we linked participants’ geocoded addresses to contaminant monitoring data [five haloacetic acids (HAA5), total trihalomethanes (TTHM), and nitrate-nitrogen (NO3-N)]. We estimated private well nitrate levels using random forest models accounting for well depth, soil characteristics, nitrogen inputs, and other predictors. We assigned drinking water source for 84% (N = 74,919) of participants. Among these, 69% of IA and 75% of NC participants used private wells; 27% in IA and 21% in NC used PWS. Median PWS nitrate concentrations (NO3-N) were higher in IA [0.9 mg/L, interquartile range (IQR): 0.4–3.1 mg/L] than NC (0.1 mg/L, IQR: 0.1–0.2 mg/L), while median HAA5 and TTHM concentrations were higher in NC (HAA5: 11.9 µg/L, IQR: 5.5–33.4 µg/L; TTHM: 37.7 µg/L, IQR: 10.7–54.7 µg/L) than IA (HAA5: 5.0 µg/L, IQR: 3.7–10.7 µg/L; TTHM: 13.0 µg/L, IQR: 4.2–32.4 µg/L). Private well nitrate concentrations in IA (1.5 mg/L, IQR: 0.8–4.9 mg/L) and NC (1.9 mg/L, IQR: 1.4–2.5 mg/L) were higher than PWS. More private wells in IA (12%) exceeded 10 mg/L NO3-N (regulatory limit for PWS) than NC (<1%). Due to the proximity of their drinking water sources to farms, agricultural communities may be exposed to elevated nitrate levels.

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Consumption of water contaminated by nitrate and its deleterious effects on the human thyroid gland: a review and update

Cited by 25 publications

References 107 publications

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Iodine as a potential endocrine disruptor—a role of oxidative stress

Drinking water sources and water quality in a prospective agricultural cohort

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