Relationships between biomarkers of exposure and neurological effects in a group of workers exposed to acrylamide.

A study was performed among 41 workers heavily exposed to a mixture of acrylamide and acrylonitrile in the city of Xinxiang, Henan province, People's Republic of China. The workers underwent a complete medical and neurological examination and provided blood and urine for the determination of several biomarkers of exposure. Among the exposed workers, signs and symptoms indicating peripheral neuropathy were found with statistically significant increased frequencies compared to a group of controls from the same city. Based on neuropathic signs and symptoms and quantifiable indicators of peripheral nervous dysfunction, such as vibration thresholds and electroneuromyography measurements, a neurotoxicity index (NIn) specific for acrylamide-induced peripheral neuropathy was designed. The NIn, which adequately predicted the clinical diagnosis of peripheral neuropathy, was significantly correlated with the levels of mercapturic acids in 24-hr urine, hemoglobin adducts of acrylamide, accumulated in vivo doses of acrylamide, employment time, and vibration sensitivity. The NIn was correlated also with hemoglobin adducts of acrylonitrile, which was explained primarily by a correlation between acrylamide and acrylonitrile exposure in this workshop. However, it was not significantly correlated with momentary measures of exposure such as concentrations of acrylamide in the air or in the plasma of exposed workers. This study is the first in which adduct monitoring has been applied to the same group of individuals in which adverse health effects have been observed. The results seem to indicate that hemoglobin adducts are useful as predictors of acrylamide-induced peripheral neuropathy and that measurements of vibration thresholds are useful for identifying early neurotoxic effects in workplaces with hazardous exposures to acrylamide.