Toenail as a biomarker of heavy metal exposure via drinking water: a systematic review

Abstract

<jats:title>Abstract</jats:title><jats:p>Toenail is metabolic end product of the skin, which can provide information about heavy metal accumulation in human cells. Slow growth rates of toenail can represent heavy metal exposure from 2 to 12 months before the clipping. The toenail is a non-invasive biomarker that is easy to collect and store and is stable over time. In this systematic review, the suitability of toenail as a long-term biomarker was reviewed, along with the analysis and validation of toenail and confounders to heavy metal. This systematic review has included 30 articles chosen from a total of 132 articles searched from online electronic databases like Pubmed, Proquest, Science Direct, and SCOPUS. Keywords used in the search included “toenail”, “biomarker”, “heavy metal”, and “drinking water”. Heavy metal in toenail can be accurately analyzed using an ICP-MS instrument. The validation of toenail heavy metal concentration data is very crucial; however, the Certified Reference Material (CRM) for toenail is still unavailable. Usually, CRM for hair is used in toenail studies. Confounders that have major effects on heavy metal accumulation in toenail are dietary intake of food and supplement, smoking habit, and overall health condition. This review has identified the advantages and limitations of using toenail as a biomarker for long-term exposure, which can help future researchers design a study on heavy metal exposure using toenail.</jats:p>

Prenatal exposure to neurotoxic metals is associated with increased placental glucocorticoid receptor DNA methylation

“…57 Parents were asked to collect their own and their children's toenail clippings from all toes and mail back the samples in provided envelopes. Average time from birth to collection was 2.8 months (range 0.3-7.1 months).…”

Estimation of exposure distribution adjusting for association between exposure level and detection limit

“…For example, in the colon cancer study measuring trace element accumulation in toenails [2], we observed a statistically significant association between the exposure level and DL in Appalachian cancer cases for at least six trace elements (Table IV). This may be because trace elements can cause adverse effects on metabolism and therefore lead to slow growth rate of toenails [3]. As a result, toenail samples obtained from individuals with high exposure to trace elements tend to have low masses and thus high DLs.…”

Chumbo e cádmio em unhas das mãos como biomarcadores de exposição subcrônica na biomonitorização de pré-escolares

“…Ambos os elementos são persistentes no ambiente (REHMAN et al 2017), sendo que a exposição ambiental a esses elementos pode se dar por diversas vias, em especial por inalação, ingestão e até mesmo contato dérmico. Seus níveis podem ser analisados por meio de coletas de amostras oriundas de matrizes ambientais (água, solo e ar), de alimentos, bem como em amostras biológicas (sangue, urina, unha, cabelo, entre outros) que, uma vez somadas, têm o potencial de fornecer dados mais completos da exposição humana (AB RAZAK et al, 2015a).…”

“…Sabe-se que tanto o chumbo quanto o cádmio podem ser tóxicos, mesmo que haja exposição em pequenas doses (KARRI et al, 2016;KIRA et al, 2016;SOARES et al, 2017;OLYMPIO et al, 2017). Ambos são mutagênicos e possuem um potencial de alterar o DNA das células, bem como atuar como disruptores endócrinos, acarretando em distúrbios no desenvolvimento (JIN et al, 2003;HENSON e CHEDRESE, 2004;IAVICOLI et al, 2009;AB RAZAK et al, 2015a;BURM et al, 2016;ATSDR, 2017b;ATSDR, 2019). Por exemplo, em relação às alterações genéticas, alguns estudos associaram o autismo em crianças com mutações no DNA, ocasionadas por exposições ambientais a EPT (WINDHAM et al, 2006;SEBAT et al, 2007;SMITH et al, 2009;KINNEY et al, 2010).…”

“…Em relação à quantificação de ambos os elementos, os níveis de chumbo reportados na maioria dos estudos epidemiológicos são mais elevados do que os de cádmio, tanto no sangue (BIBI et al, 2015;OLYMPIO, 2018), quanto nas unhas (WILHELM et al 1991;1994;WERE et al 2008;SANDERS et al 2014;AB RAZAK et al, 2015a;BIBI et al, 2015;MERAMAT et al, 2016;APPLETON et al, 2017). Conforme o esperado, o presente estudo também obedeceu a ordem Pb > Cd, corroborando com o encontrado nos estudos de exposição a ambos os elementos indicados acima.…”