Assessment of Exposure to Heavy and Carcinogenic Metals in Heavy Metal Refining Processes

Ewa, Gaweda

Department of Aerosol Hazards / Central Institute for labour protection– National Research Institute / Czerniakowska 16/ 00-701 Warsaw, Poland

48 22 623 46 98/ ewgaw@ciop.p

ABSTRACT

The results of measurements of concentrations of harmful chemical agents in workplace air at heavy metal refining workstations in 2 Polish plants (copper and non- ferrous metal smelters) are presented. Concentrations of Ni, Cd, Ag, Cu, As, Se and Pb were determined by atomic absorption spectrometry (AAS) with graphite tube, whereas Fe, Zn, Ca by AAS with air-acetylene flame, and sulfuric acid by spectrophotometric method, and dust (total and respirable fraction) by gravimetry. Samples were taken using membrane filters and mineralized in nitric acid.

An examination of the results leads to the conclusion that risk posed by chemical substances in the examined plants varies. Hazards are significant in lead and cadmium refining processes and very small in copper electrorefining. It seems that lead constitutes the main problem in heavy metal refining processes. Exposure factors of lead in workplace air are often much higher than Polish MAC.

Keywords

Metals and metalloids, heavy metal refining processes, assessment of occupational exposure

INTRODUCTION

The aim of the study has been to assess and reduce occupational risk connected with workers’ exposure in heavy metal refining processes (lead, zinc, cadmium, copper and nickel refining). The measurements of chemical agents in workplace air constitute the basis of this assessment.

People employed in heavy metal refining processes are primarily exposed to metals and metalloids (arsenic, selenium) and their compounds, and metal compounds (iron oxides, CaO), some of which are very toxic (e.g. lead), others also carcinogenic (cadmium, nickel, arsenic). They are also exposed to such agents as industrial dusts (below 50% SiO2), sulphuric acid (nickel production, and copper electrorefining).

In Poland, the problem of exposure to harmful chemical agents in heavy metal refining processes mostly affects workers in big enterprises.

Methodology

Methods of measurement:

• Atomic absorption spectrometry with graphite tube and Zeeman background correction – As, Cd, Se, Ni, Cu, Pb, Ag [5]
• Atomic absorption spectrometry with airacetylene flame – Zn (interpretation of the results in relation to Zn Polish Maximum Admissible Concentration value Polish MAC value), Fe (to iron oxides – Polish MAC), Ca (to CaO Polish MAC) [7]
• Polish Standard PN91/Z04056/02 – sulphuric acid [3]
• Gravimetric method – industrial dust.

Air sampling

• personal sampling (flow rate – 1.2-1.8 l/min; sample  collecting  time: from 15  to 360 min)

Collection of air samples was performed according to the principles in European (EN 689: 1995) and Polish Standards (PN EN 689: 2002 [1]; PN-04008-7: 2002 [3]),which make it possible to assess compliance of working conditions with Polish MAC and Polish MAC-STEL values.

The air samples collected on nitro cellulose membrane filters (pore size – 0.85 µm) were treated with concentrated nitric acid (temperature – 140 OC) to ash the organic and inorganic matrix and to dissolve the metals present in the sample. The content of elements was determined in a 0.1 mol/l HNO3 solution [2].

RESULTS OF MEASUREMENTS

Approximately 60 workstations in 2 Polish enterprises were examined (Plant I and Plant II) [6].

Plant I – copper smelter (about 1500 workers employed in the production process) Processes carried out: lead refining, copper refining, silver refining, nickel sulphate production, copper electro refining

Plant II – non-ferrous metal smelter (about 400 workers employed in the production process)

Processes carried out: zinc refining, lead refining, cadmium refining.

The results of the determination of harmful chemical agents in air samples are presented in tables 1-2.

Table 1. Weighted average concentrations (exposure factors) of chemical agents in air samples collected at Plant I workstations.