Predicting Blood/Air Partition Coefficients of Paint Thinner Ingredients and Assessing Their Inhalation Exposure Hazards

Paint thinners constitute a large variety of volatile organic compounds that pose inhalation exposure hazards to painters. Blood/air partition coefficients (K_ba) of the volatile organic compounds play a vital role in health risk assessment following their exposure through the inhalation route. However, experimentally determined K_ba values of the thinner ingredients are very limited. Here, we estimated the K_ba for a wide range of thinner ingredients (78 compounds; across various chemical classes) using quantitative property-property relationship (QPPR) models. Nearly 50% of these compounds lack an occupational exposure limit, e.g., threshold limit value (TLV) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). Our results reveal that K_ba of hydrocarbons (log K_ba ranges from −0.56 to 3.48; with mean: 1.33 and median: 1.51) is comparatively lower than that of polar ingredients (log K_ba ranges from 0.92 to 4.37; with mean: 2.88 and median: 2.93). Among the hydrocarbons, aromatic hydrocarbons show higher values of K_ba than aliphatic hydrocarbons (log K_ba ranges from −0.56 to 1.56 for aliphatic vs. 1.17 to 3.48 for aromatic). Moreover, the molecular structure and chain length of aliphatic hydrocarbons are observed to have a strong influence on their K_ba values. Further, we estimated the respiratory absorption factor (RAF) of the thinner ingredients, which is a crucial parameter in determining the actual inhalation dose. Comparative analysis of the K_ba and RAF facilitated the identification of several compounds that pose potential inhalation exposure hazards, although these compounds lack a TLV. The findings of this study will be useful in selecting safer thinner products and implementing suitable environmental and workplace interventions, such as engineering and personal controls for hazardous thinner products, to minimize harmful chemical exposure to painters. Additionally, these findings will aid in prioritizing chemicals for experimental health risk assessment of paint ingredients.