The ion-aerosol balance equations are solved to study the effect of aerosol concentration on electrical conductivity for different ionization rates taking bimodal lognormal size distribution for the grand average continental aerosol particles and using size dependent attachment and coagulation coefficients for the aerosol particles. The results show that the inverse relationship between the polar conductivity and aerosol concentration exists only up to a certain critical value of aerosol concentration which depends upon the prevailing ionization rate. Further increase in aerosol concentration causes an increase in polar conductivity due to the contribution made to it by large ions. However, this increase in conductivity is again restricted by recombination of charged aerosols in a highly polluted atmosphere. Further, it is shown that in polluted urban environments where particulate concentration is large and variable the charge equilibrium is attained faster when the effect of recombination of charged aerosols is included. ¿ 1997 American Geophysical Union