Characterization of nickel levels considering seasonal and intra-individual variation using three biological matrices.

Nickel compounds are classified as group 1 carcinogens by the International Agency for Research on Cancer. However, only a few exposure assessment studies have been conducted on such compounds to date. In this study, we investigated the distribution of nickel in three biological types of samples (blood, serum, and urine) and its temporal variability through repeated measurements. From 2020 to 2021, blood and urine samples were collected for four times from 50 healthy participants. Nickel concentrations were determined using inductively coupled plasma mass spectrometry, and inter-individual correlation was calculated from linear mixed model. The overall geometric mean of nickel was 1.028 µg/L in blood, 0.687 µg/L in serum, and 1.464 µg/L in urine. Blood nickel was the highest in November (blood: 1.197 µg/L), and the geometric mean of nickel concentrations in the serum and urine were the highest in March (serum: 1.146 µg/L; urine: 1.893 µg/L). This matched seasonal trends for fine particulate matter concentrations from 2020 to 2021. Thus, seasonal effects significantly affect nickel levels in blood, serum, and urine. The inter-individual correlations were low as 0.081 for blood and 0.064 for urine. In addition, the correlation of nickel levels between each biological sample was low. It was also found that age, gender, commuting time, and different matrices affect concentrations. Blood and serum nickel levels were high in this study compared to other nationwide data, with urinary nickel ranking the second highest among the six countries examined. Therefore, biomonitoring study in the general population should be conducted, and finding a suitable matrix that can reflect nickel exposure to set exposure guideline levels is imperative.

Effects of Hyperbaric Oxygen Therapy on Inflammation, Oxidative/Antioxidant Balance, and Muscle Damage after Acute Exercise in Normobaric, Normoxic and Hypobaric, Hypoxic Environments: A Pilot Study.

The purpose of this study was to investigate the effects of hyperbaric oxygen therapy (HBOT) on inflammation, the oxidative/antioxidant balance, and muscle damage after acute exercise in normobaric, normoxic (NN) and hypobaric, hypoxic (HH) environments. Eighteen healthy males were selected and randomly assigned to three groups: exercise in NN conditions (NN group, n = 6), HBOT treatment after exercise in NN conditions (HNN group, n = 6), and HBOT treatment after exercise in HH conditions (HHH group, n = 6). All subjects performed treadmill running for 60 min at 75-80% maximum heart rate (HRmax) exercise intensity under each condition. The HBOT treatments consisted of breathing 100% oxygen at 2.5 atmosphere absolute (ATA) for 60 min. Blood samples were collected before exercise (BE), after exercise (AE), and after HBOT (AH) to examine inflammation (fibrinogen, interleukin-6 [IL-6], and tumor necrosis factor-α (TNF-α)), the oxidative/antioxidant balance (derivatives of reactive oxygen metabolites (d-ROMs) and the biological antioxidant potential (BAP)), and muscle damage (creatine kinase (CK) and lactate dehydrogenase (LDH)). Plasma fibrinogen, serum IL-6, CK, and LDH levels were significantly increased AE compared to BE in all groups (p < 0.05). Plasma fibrinogen levels were significantly decreased AH compared to AE in all groups (p < 0.05), and the HNN group had a significantly lower AH compared to BE (p < 0.05). Serum IL-6 levels were significantly decreased AH compared to AE in the HNN and HHH groups (p < 0.05). Serum CK levels were significantly decreased AH compared to AE in the HHH group (p < 0.05). Serum LDH levels were significantly decreased AH compared to AE in the HNN and HHH groups (p < 0.05), and the NN and HNN groups had significantly higher AH serum LDH levels compared to BE (p < 0.05). These results suggest that acute exercise in both the NN and HH environments could induce temporary inflammatory responses and muscle damage, whereas HBOT treatment may be effective in alleviating exercise-induced inflammatory responses and muscle damage.