###### Abstract  
Introduction: We assessed the impact on metal levels of seafood, mollusk and fish consumption (SMFc) before urine and toenail sample donation among workers exposed to metals. Methods: This is a cross-sectional epidemiological study with 101 workers from the chemical and metal industry and 40 unexposed workers from the services sector. We measured urinary (As, Ba, Be, Cd, Co, Cu, Hg, Li, Mo, Pb, Se, Sr, Tl, V, W and Zn) and toenail (same plus Al, Cr, Fe, Mn, Ni and U) metal levels. Results: Urinary arsenic levels were higher among workers eating seafood or mollusks (102 ppm vs. 55.4 ppm; \(p=0.042\)) or fish (109 ppm vs. 48 ppm; \(p=0.007\)) 8 h before sample donation. Urinary mercury was associated with consumption of blue fish (11.865 ppm) and canned sardines (19.125 ppm) (\(p=0.028\)). With respect to teenals, fish consumption was associated with aluminum (17 ppm vs. 8.6 ppm; \(p=0.012\)) and beryllium (5 ppb vs. 1 ppb; \(p=0.017\)). Arsenic urinary levels were associated with numbers of hours prior to sample collection since latest SMFc (\(p=0.001\)). Conclusion: Among workers exposed to metals, seafood, mollusk and fish consumption is an important determinant of urinary arsenic levels, as sea fish for urinary mercury, but not for other metals. fish, mollusk and seafood consumption; urine; toenail; metal levels; workers; heavy metals  
homeostasis of a particular essential element [6; 7]. Moreover, toxic metals do not remain in the body easily; the majority of them are expelled from the body through sweat, urine and feces. However, if organic/inorganic compounds have been formed, they accumulate mainly in bones, myocardial tissue, internal parenchymal organs, skin, nails and hair [1; 8]. Thus, the effects on the human body vary depending on both the characteristics of each metal and the affinity of each tissue [9; 10]. As, Pb and Hg lead the podium of the Agency for Toxic Substances and Disease Registry (ATSDR) 2022 substance priority list [11]. Cd ranks seventh, and it is the third inorganic substance. Among the most important human health effects due to exposure to metals, we can find cancer [12], cardiovascular diseases [13] and neurotoxicity [14]. These elements can enter the human body via three main routes, namely inhalation, transdermal adsorption and ingestion [15; 16]. Dietary intake, including food, drinking water, soil and dust ingestion, are the main source of exposure to metals in the general population [17], although recent studies have reported that levels of ingestion in daily foods are lower compared to inhalation exposure via airborne particles, the main exposure pathway [15; 16]. Among metal, chemical and mining workers, occupational exposure would be the most important source through the inhalation and transdermal adsorption of dust and airborne particles [18]. Occupational exposure to metals is more frequent than what initially could be expected, in both the environmental and the occupational settings [19; 20]. Hair, nails, blood, umbilical cord urine, feces, placenta and breast milk are commonly used biomarkers in research of contamination risks to human health [21]. Urine, saliva and blood samples offer short-term exposure (24 h), and are largely influenced by diet [22; 23; 24]. Urine biomonitoring of metal levels among workers is a simple, non-invasive and common way to monitor levels of such elements in the occupational environment [25]. On the other hand, nails and hair have been used as internal exposure indicators and may reflect the long-term (6 \(\pm\) 18 months) patterns of mineral metabolism [26; 27; 28]. Furthermore, the advantage of using toenails as a biomonitoring tool is that unlike hair or fingernail samples, it reduces the likelihood of external contamination [27; 28; 29; 30]. There is not a single biological matrix that is the best option for metal biomonitoring. Urine is the most commonly used biomarker of exposure across metals with some exceptions like lead exposure [21; 28].