Logarithmic Scale and Pollutant Concentration

The signal level, $S$, from a pollutant monitoring instrument is determined by the equation $S=\log_{10}(C)$, where $C$ represents the pollutant concentration in $\mu g/L$. If one lake has a signal level of 1.2 and another has a signal level of 1.8, by what approximate factor is the pollutant concentration in the second lake greater than in the first?