Urinary elimination of nickel and cobalt in relation to airborne nickel and cobalt exposures in a battery plant

Objective To estimate the relationship between Ni concentrations in the ambient air and in the urine, at a battery plant using nickel hydroxide. Methods Workers occupationally exposed to a mixture of nickel hydroxide, metallic cobalt and cobalt oxyhydroxide dust were studied during two consecutive workdays. Air levels of Ni and Co in total dust were determined by personal sampling in the breathing zone. Both metals in air were sampled by Teflon binder filters and analyzed by inductively coupled plasma absorption emission spectrophotometry. Urine was collected from 16 workers immediately before and after the work shift. Urinary Ni and Co concentrations were measured by electrothermal atomic absorption spectrometry. Results A poor correlation was seen between Co in the air and in post-shift urine (r = 0.491; P < 0.01), and no correlation was found between Ni in the air and in post-shift urine (r = 0.272; P = 0.15), probably due to the use of respiratory protection. The subjects were exposed to higher levels of Ni than Co (Ni (mg/m³) = −0.02 + 7.41 Co (mg/m³), r = 0.979, P < 0.0001). Thus, exposure to Co at 0.1 mg/m³ should produce a Ni level of 0.7 mg/m³. According to section XIII of the German list of MAK and BAT Values, a relationship between exposure to Co and urinary Co excretion, Co (μg/l) = 600 Co (mg/m³), has been established and the relationship between soluble or insoluble Ni salts in the air and Ni in urine was as follows: Ni (μg/l) = 10 + 600 Ni (mg/m³) or Ni (μg/l) = 7.5 + 75 Ni (mg/m³). Assuming nickel hydroxide to be soluble and to be insoluble, the Ni concentrations corresponding to Ni exposure at 0.7 mg/m³ were calculated as 430 and 60 μg Ni/l, respectively. Similarly, exposure to Co at 0.1 mg/m³ should result in Co urinary concentrations of 60 μg Co/l. On the other hand, a good correlation was found between Co and Ni in post-shift urine (Ni (μg/l) = 9.9 + 0.343 Co (μg/l), r = 0.833, P < 0.0001). On the basis of this relationship, the corresponding value found in our study was 0.343 × 60 μg Co/l + 9.9 = 30.5 μg Ni/l. This value was close to that calculated by the equation for a group of insoluble compounds, but about 14 times lower than that calculated by the equation for a group of soluble compounds. Conclusions Our results suggest that exposure to nickel hydroxide yields lower urine nickel concentrations than the very soluble nickel salts, and that the grouping of nickel hydroxide might be reevaluated. Therefore, to evaluate conclusively the relationship between nickel hydroxide dust in the air and Ni in post-shift urine, further studies are necessary.