Rapid Review of Dermal Penetration and Absorption of Inorganic Lead Compounds for Occupational Risk Assessment

Abstract

Lead (Pb) exposure continues to be a significant public health issue in both occupational and non-occupational settings. The vast majority of exposure and toxicological studies have focused on effects related to inhalation and gastrointestinal exposure routes. Exposure to inorganic Pb compounds through dermal absorption has been less well studied, perhaps due to the assumption that the dermal pathway is a minor contributor to aggregate exposures to Pb compounds. The aim of this rapid review was to identify and evaluate published literature on dermal exposures to support the estimation of key percutaneous absorption parameters (Kp, flux, diffusion rate) for use in occupational risk assessment. Eleven articles were identified containing information from both in vitro and in vivo systems relevant to percutaneous absorption kinetics. These articles provided 24 individual study summaries and information for seven inorganic Pb compounds. The vast majority of study summaries evaluated (n = 22, 92%) reported detectable amounts of dermal absorption of inorganic Pb. Data were identified for four Pb compounds (Pb acetate, Pb nitrate, Pb oxide, and Pb metal) that may be sufficient to use in evaluating physiologically based pharmacokinetic models. Average calculated diffusion rates for the pool of animal and human skin data ranged from 10−7 to 10−4 mg cm−2 h−1, and Kp values ranged from 10−7 to 10−5 cm h−1. Study design and documentation were highly variable, and only one of the studies identified was conducted using standard test guideline-compliant methodologies. Two studies provided quality estimates on the impacts of dermal absorption from water-insoluble Pb compounds on blood Pb levels. These two studies reported that exposures via dermal routes could elevate blood Pb by over 6 µg dl−1. This estimation could represent over 100% of 5 µg dl−1, the blood Pb associated with adverse health effects in adults. The utility of these estimates to occupational dermal exposures is limited, because the confidence in the estimates is not high. The literature, while of limited quality, overall strongly suggests inorganic Pb has the potential for dermal uptake in meaningful amounts associated with negative health outcomes based on upper bound diffusion rate estimates. Future standard test guideline-compliant studies are needed to provide high-confidence estimates of dermal uptake. Such data are needed to allow for improved evaluation of Pb exposures in an occupational risk assessment context.

Occupational Exposure among Electronic Repair Workers in Ghana

“…Occupational exposure routes to metals such as Pb, Sn and Cd may include inhalation, transfer from hand to mouth with subsequent gastrointestinal exposure and skin absorption [ 49 , 50 , 51 , 52 ]. Hand hygiene among workers handling electronic equipment may be a source of the enhanced B-Pb, B-Cd and U-Sn, as 81% of the electronic repair workers and 78% of the control group reported that they did not wash their hands with soap before eating [ 8 ].…”

“…Acid matrix-matched multielement calibration standards were prepared by dilution of certified primary standards (Spectrapure Standards AS, Oslo, Norway). The following isotopes were measured (oxygen reaction mass shift is marked with r, on-mass was measured otherwise): 75r As, 209 bismuth (Bi), 114 Cd, 140r Ce, 59 Co, 63 copper (Cu), 52 Cr, 153r Eu, 158r Gd, 69 gallium (Ga), 202 Hg, 56 iron (Fe), 139r La, 55r manganese (Mn), 144r Nd, 60 Ni, 206+207+208 Pb, 195 platinum (Pt), 141r Pr, 121 Sb, 45r Sc, 107 silver (Ag), 120 Sn, 159r Tb, 203 thallium (Tl), 51r vanadium (V), 182 tungsten(W), 89r Y and 66 zinc (Zn). The element concentrations of Pb were calculated using the sum of the isotopic net signals (marked with +).…”

Relationship between Lead Exposure and Genotoxic Effect in Paint Industry Workers

“…Although inorganic Pb exposure to the dermal route is rarely studied because it contributes little to absorption (Wani et al, 2015), several absorption kinetics parameters, such as Kp and diffusion rate, are produced to be used as a risk assessment for the work environment. The study produced Kp of 10 -7 -10 -5 cm.hour -1 and diffusion rate ranges of 10 -7 -10 -4 mg.cm -2 .hour -1 obtained from animal and human skins (Niemeier et al, 2022). After absorption, lead accumulates in the blood, soft tissues, and bone, and the lead's half-life in these parts is 35 days, 40 days, and 20-30 years respectively (Sangeetha and Umamaheswari, 2020).…”