Chee-Ching Sun et al

Percutaneous Absorption of Inorganic Lead Compounds

AIHA Journal 63:641-646. Chee-Ching Sun, Ten-Tsao Wong, Yaw-Huei Hwang, Kun-Yu Chao, Shiou-Hwa Jee, and Jung-Der Wang. 2002

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The aim of this study is to investigate whether dermal exposure to lead dusts might contribute to increased lead absorption into the body. In order to carry out this investigation, the lead content on the skin surface (dorsal hand and lower back) of 10 lead-battery workers was measured by the method of ten repeated skin strips, along with blood lead measurements. The authors investigated the correlation between dermal and blood lead measurements. In addition, urinary lead content of rats was measured after epicutaneous application of four lead compounds: lead sulfate, lead oxide, lead powder and lead stearate.

The results show that there was a decreasing amount of lead content in the exposed skin going from the outer to the inner layer. Further investigation of the dorsal hand exposure shows that the lead content on the first and second layer of the skin differs greatly from the subsequent layers in most of the workers. This data raises some questions as to the effectiveness of lead absorption through the skin as, from the results, lead particles seem to stay on the outer layer of the skin. Another concern is the correlation between the lead content on the outer layer of the skin and the blood lead content. The lead content on the first and second layers of the skin is less well correlated with the blood lead content than the innermost skin layers, which is in some way questionable since it is more logical if the blood lead content correlates best with the lead content on the innermost layer.

The results also show that the total amount of lead in the dorsal hand was linearly correlated with the blood lead content, but not in the lower back. Further interpretation of the data shows that there was a significant difference in the total lead content between the dorsal hand and the lower back. However, it should be noted that the measurements do not take into account the total surface area of the dorsal hand compared with the lower back (which probably represents the contamination on the covered parts of the body). The units used to represent the lead content for both cases is µg, although the authors should have calculated the lead content on the sample(µg) divided by the area of the sample (12 cm2) multiplied by the total surface of dorsal hands or the remainder of the body. If this calculation is done, there is a strong possibility that the total amount of lead in the skin represented by the lower back would exceed that in the hands.

In the animal study, 100 mg of lead in petrolatum on a 2 x 6 cm cloth was applied on the shaven skin of rats. The application of petrolatum would affect the natural absorption mechanism of lead on the skin since the lead compound would first dissolve into the petrolatum and then partition into the skin. The natural absorption, which relate more to actual exposure of lead in human, can be achieved by directly apply the lead particles on the skin. Another factor that should be alerted is the possible absorption of some of the lead particles into the cloth.

Overall, dennal exposure to lead dusts can be considered a significant contributing factor to the total lead absorption into the body and is a real concern in industries which lead is one of their main chemicals. The authors' approach in evaluating dennal exposure to lead dusts can be further enhanced in order to determine a more accurate and reliable measurement.

Review by Zulfakir Said, University of Aberdeen

The views and opinions expressed in the text are solely of the review author

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