1 In general, the total dissolved solids concentration is the sum of the cations (positively charged) and anions (negatively charged) ions in the water.  Parts per Million (ppm) is the weight-to-weight ratio of any ion to water.
If you refrigerate the rice, and you want to eat it cold, its perfectly fine. People eat cold rice salads all the time. Cold rice pudding is fine. Its just sitting around at room temperature that is the problem.
Do not allow cooked food to sit out at room temperature for an extended period, two hours is maximum for proper food safety. For a long term option, you can freeze your dry rice while preserving its taste if you use an oxygen-free (oxygen is the source of freezer burn) freezer safe container. Cooked rice may also be frozen, but it is not recommended since it will most likely become mushy when re-heated.