UC San Diego

Draize eye scores (DES) for 37 pure organic liquids have been converted into scores for the corresponding vapours, DES/P^o, where P^o is the liquid vapour pressure in ppm at 298 K. It is shown that there is a constant difference (0.66) between values of log(DES/P^o) and log(1/EIT) where EIT is the eye irritation threshold in ppm of eight vapours towards human subjects. The 37 log(DES/P^o) values can be combined with 17 log(1/EIT) values to give one quantitative structure-activity relationship,

Log SP = -7.918 – 0.482 R₂ + 1.420 p₂ ^H   + 4.025 ∑a^H ₂   + 1.219 ∑b₂ ^H   + 0.853 log L¹⁶          [i]

n = 54, r² = 0.928, r² _CV = 0.913, sd = 0.36, F = 124

where R₂ is an excess molar refraction, p₂ ^H is the compound polarizability/dipolarity, ∑a^H ₂ and ∑b₂ ^H are the compound hydrogen-bond acidity and basicity, and L¹⁶ is the gas-hexadecane partition coefficient. The number of data points is n, the correlation coefficient is r, the standard deviation is sd, and F is the F-statistic. LogSP is then either [log(DES/P^o) - 0.66], or log(1/EIT). It is suggested that equation i can be used to predict eye irritation of organic vapours and pure liquids as eye irritation thresholds.