From China Digital Space

毒大米 (dú dà mǐ): poison rice

"Poison rice" is rice that has been treated to increase its marketability. Old rice (chenmi) is polished, treated with chemicals and coated with paraffin. This gives the rice a desirable translucent appearance. Unfortunately, the treated rice causes negative health effects. For more on this topic, please read Netizen: List of Toxic Foods You Need to Know.