Air to brain, blood to brain and plasma to brain distribution of volatile organic compounds: linear free energy analyses.

Partition coefficients, K(brain), for volatile organic compounds, VOCs, from air to brain have been collected for 81 compounds (air to human brain and air to rat brain). For the 81 VOCs a linear free energy equation (LFER) correlates log K(brain) with R(2) = 0.923 and S.D. = 0.346 log units. Use of training and test sets gives a predictive assessment of 0.35-0.40 log units. Combination of log K(brain) with our previously listed values of log K(blood) enables blood to brain partition, as log P(b-brain), to be obtained for 78 VOCs. These values can be correlated with R(2) = 0.725 and S.D. = 0.203 log units; use of training and test sets allows a predictive assessment for log P(b-brain) of 0.16-0.20 log units. Values for air to plasma were available for 21 VOCs. When these data were combined with the data on air to blood and air to brain, values for partition between (blood or plasma) to brain, P(bp-brain), were available for 99 VOCs. A LFER correlates this data with R(2) = 0.703 and S.D.=0.197 log units; use of training and test sets allows a predictive assessment for log P(bp-brain) of 0.15-0.20 log units.