Early neurotoxic effects of inhalation exposure to aluminum and/or manganese assessed by serum levels of phospholipid-binding Clara cells protein

Abstract

Little is known on the disturbances of lung epithelium function in aluminum casting smelters and shipyard welders exposed by inhalation to irritant occupational pollutants, dust and fumes. The exact mechanism of aluminum and manganese toxicity is not known, but it is thought that they may potentiate oxidative and inflammatory stress, leading to impaired neurological function. The aim of the study was to investigate the subclinical effects of aluminum and manganese exposure on the nervous system and to assess their relationship to the biomarkers of exposure and effect in workers exposed to neurotoxic fumes. The relationship between the neurological and respiratory effects was investigated in 50 workers at aluminum casting smelters exposed to x_GM = 0.29 Al₂O₃ mg m^{− 3}, and 59 shipyard welders exposed to x_GM = 0.16 Mn mg m^{− 3}, and the reference group. Serum anti-inflammatory, phospholipid-binding Clara cell protein (CC16) as a peripheral marker of the bronchiolar epithelium function measured. The lowest CC16 concentrations were found in workers showing subjective CNS symptoms and abnormal neurophysiological findings: EEG and visual evoked potentials. A strong inverse relationship was found between serum Al (Al-S) and CC16 concentrations (p = 0.006). Younger smelter workers and welders, with a shorter exposure duration, presented a higher number of VEPs than the workers employed for a longer period of time. The sub-clinical neurological symptoms (VEP) and low CC16 level can be associated with an internalization of Al ions with lipid fractions of the lung epithelium, which in turn may help Al ions overcome the blood–brain barrier. The inhibited secretion of anti-inflammatory Clara cell protein and low respiratory performance in younger Mn welders was found to enhance subclinical neurotoxic symptoms, especially VEPs, related to exposure to airborne Mn and Mn-B.

Keywords:

• Clara cells protein
• aluminum
• manganese
• neurotoxicity
• inhalation

Acknowledgments

This study was supported by the Polish State Committee for Scientific Research, Grant PB 725/P05/2000/18 KBN for aluminum effects study and Grant PB 649/P05/97/12 KBN for welders exposure study. We wish to express appreciation to Prof. M. Jakubowski, Principal Coordinator of Grant PB 457/P05/95/8 KBN under which the neurological examinations of welders were performed. Thanks are also due to Dr. J. Gruchala for spirometric examination, Dr. W. Matczak for Al and Mn determination in the air, Dr. M. Ochocka-Trzcinka and G. Razniewska, MA, for Al and Mn determinations in urine and serum. We also would like to thank Ms. A. Kubiak for technical assistance and Dr. W. Szymczak for statistical analysis of results.

This paper was presented at the SETAC Asia/Pacific 2006 conference held at Peking University, China on September 18–20, 2006.

Notes

*P < 0.05 vs. reference; ND = no data available.

*P < 0.05 vs. reference.

* P < 0.05 vs. reference; ND = no data available.