Table 3.

Metal concentrations (µg/g creatinine) in urine [geometric means (25th–75th percentiles)] from schoolchildren and children working in surgical instruments manufacturing units.

Schoolchildren (n = 74)	Working children (n = 94)	Reference values according to NHANES (age group)b
		Urinary metals	p-Valuea	6–11 years	12–19 years	6–88 years
Creatinine (g/L)	1.08 (0.80–1.30)	0.83 (0.5–1.03)	0.0008
Al	24.8 (17.4–28.0)	31.9 (19.5–47.4)	0.01
V	0.85 (0.65–1.17)	1.43 (0.88–2.14)	< 0.0001
Cr	0.66 (0.40–0.82)	30.1 (12.3–78.2)	< 0.0001	0.12 (0.23–0.60)
Mn	2.94 (1.90–3.97)	4.22 (2.04–7.12)	0.02	0.48 (1.16–2.42)
Co	1.09 (0.70–1.76)	1.30 (0.74–2.10)	0.1	0.53 (0.69–1.30)	0.33 (0.50–0.95)
Ni	6.02 (4.54–7.90)	9.87 (6.76–13.8)	< 0.0001
Cu	17.6 (14.9–20.2)	22.1 (16.0–31.0)	0.004
Zn	394.0 (274.0–554.0)	402.0 (294–561)	0.7
As	20.0 (17.3–24.0)	19.2 (14.2–26.0)	0.8	8.25 (11.7–40.1)	6.11 (9.66–27.8)
Se	44.7 (36.8–56.0)	54.9 (42.8–73.2)	0.006
Mo	131.0 (96.2–190)	234.0 (145–409)	< 0.0001	72.5 (101–160)	37.5 (53.2–81.0)
Cd	0.56 (0.43–0.72)	0.66 (0.49–1.0)	0.05	0.09 (0.12–0.31)	0.08 (0.12–0.23)
Sn	0.05 (0.01–0.14)	0.20 (0.11–0.44)	< 0.0001	2.84 (5.01–16.1)
Sb	0.04 (0.01–0.10)	0.22 (0.16–0.37)	< 0.0001	0.11 (0.16–0.33)	0.07 (0.10–0.19)
Ba	5.13 (3.55–7.57)	4.44 (2.58–6.0)	0.3	2.58 (4.45–10.3)	1.54 (2.60–6.47)
Pb	5.70 (4.10–8.0)	5.68 (3.85–8.42)	0.6	0.92 (1.45–3.47)	0.43 (0.62–1.23)
U	0.085 (0.061–0.101)	0.124 (0.064–0.187)	0.009	0.009 (0.013–0.033)	0.007 (0.01–0.034)
Values in µg/g creatinine after exclusion of creatinine values < 0.3 g/L ap-Values from a model adjusted for age, height, and weight. bU.S. National Health and Nutrition Examination Survey: geometric mean (75th–95th percentile). Values for 6–11 years and 12–19 years from Centers for Disease Control and Prevention (2009); values for 6–88 years from Paschal et al. (1998).