Table 5: Changes in element concentrations in tap water after running the machine with participants feet.

Elements (μg/L)Pre-FBS ( 𝑛 = 6 )Post-FBS ( 𝑛 = 2 4 )Post-FBS FF–Pre-FBS 𝑃 v a l u e
Mean ± Std devMean ± Std devDifference ± Std dev%change

Aluminum§110.80 ± 51.79126.75 ± 44.055.00 ± 58.434.50.239
Antimony§1.00 ± 1.411.71 ± 1.521.21 ± 1.50120.80.056
Arsenic§1.00 ± 0.006.58 ± 1.025.58 ± 1.02558.30.0001
Barium§22.00 ± 4.4726.04 ± 4.896.04 ± 4.8927.50.034
Boron40.00 ± 10.0041.13 ± 6.314.04 ± 9.1210.10.118
Cadmium§0.80 ± 1.108.54 ± 2.558.04 ± 2.801,005.2< 0.0001
Calcium39,316.00 ± 617.3639,091.46 ± 1,198.06−231.04 ± 1,354.99−0.60.250
Chromium1.60 ± 2.0723,548.21 ± 4,783.0923,546.21 ± 4,782.521,471,638.0< 0.0001
Cobalt1.00 ± 0.00332.05 ± 57.69331.05 ± 57.6933,105.0< 0.0001
Copper406.00 ± 190.34836.71 ± 152.62456.71 ± 318.01112.5< 0.0001
Iron388.60 ± 178.33114,629.83 ± 23,404.94114,200.08 ± 23,447.2229,387.6< 0.0001
Lead§2.40 ± 1.142.50 ± 0.780.00 ± 0.780.00.607
Lithium1.40 ± 1.952.00 ± 2.300.25 ± 0.9417.90.985
Magnesium10,647.60 ± 315.7010,600.83 ± 398.56−128.67 ± 509.11−1.20.218
Manganese5.20 ± 0.451,643.83 ± 275.351,638.58 ± 275.2631,511.2< 0.0001
Molybdenum48.00 ± 48.793,575.50 ± 569.093,515.50 ± 567.167,324.0< 0.0001
Nickel2.00 ± 2.1215,946.42 ± 2,770.4215,943.92 ± 2,769.51797,195.8< 0.0001
Phosphorus26.60 ± 9.8170.29 ± 26.7944.29 ± 26.82166.50.004
Potassium2,118.00 ± 132.362,586.71 ± 171.82489.21 ± 162.1823.1< 0.0001
Selenium0.22 ± 0.441.04 ± 0.690.77 ± 0.64348.50.032
Silicon634.00 ± 217.551,933.38 ± 250.561,338.38 ± 238.36211.1< 0.0001
Silver§0.000.000.000.00.000
Sodium96,458.00 ± 8,298.7595,941.42 ± 8,473.96−1,958.58 ± 6,064.23−2.0< 0.0001
Strontium204.80 ± 14.24190.83 ± 12.16−11.67 ± 9.95−5.70.070
Sulfur9,858.00 ± 2,707.588,685.71 ± 1,471.65−496.79 ± 2,448.86−5.00.512
Uranium§0.20 ± 0.450.29 ± 0.460.04 ± 0.3620.80.851
Vanadium0.60 ± 0.5559.96 ± 12.7059.04 ± 12.669,840.3< 0.0001
Zinc18.00 ± 8.3734.13 ± 8.7816.63 ± 7.6592.40.001

Total160,313.82 ± 7,685.23319,923.84 ± 37,781.00158,783.82 ± 34,556.2199.0< 0.0001

Array components1,486.40 ± 7,702.91160,512.55 ± 31,630.27160,970.43 ± 31,896.7010,829.5< 0.0001
Essential elements158,689.22 ± 368.55159,238.88 ± 9,413.96−2,212.53 ± 8,230.33−1.40.8013
PTEs§138.20 ± 49.37172.42 ± 41.3825.92 ± 58.4618.80.0423

§PTEs: potentially toxic elements were defined to be aluminium, antimony, arsenic, barium, cadmium, lead, silver, and uranium.
Essential elements were defined to be boron, calcium, lithium, magnesium, phosphorus, potassium, selenium, sodium, strontium, sulphur, vanadium, and zinc.
Array components were defined to be chromium, cobalt, copper, iron, manganese, molybdenum, nickel, and silicon.
Bold indicates a statistically significant difference, 𝑃 < 0 . 0 5 (Mann-Whitney U test).