Abundance determination from emission line nebulae plays a vital role in understanding stellar evolution and galactic chemical evolution. Elemental abundances are traditionally derived from recombination and collisionally excited line fluxes by employing appropriate ionization correction factors for those unseen ions. These methods assume that the stellar radiation is fully absorbed by gas alone and the temperature and density structures in the nebula are uniform, both are far from reality. It has been realized that grains in ionized gas compete with gas effectively in absorbing the ionizing radiation and significantly reshape the nebular thermal structure. Observationally it has been found that ionized nebula show temperature fluctuation, which could arise from dust heating. Most challenging problem today in nebular astrophysics is that the heavy element abundances derived from collisionally excited lines are systematically lower than those obtained from recombination lines, termed as the abundance discrepancy factors (ADF). This puts an important question 'which are right abundances of PNe and ISM?'. Temperature fluctuation can cause such an effect. We propose that incorporating grain heating in ionized gas by considering the interaction of gas and dust with stellar radiation accurately could resolve both the temperature fluctuation and ADF of the ionized gas; which could cause lower emphirical abundances. Our recent results obtained with CLOUDY models of a few PNe will be discussed on these lines.