#### Answer

100

#### Work Step by Step

According to the question, January 1 of the base year is represented by $x=0$. Therefore, we substitute $x=0$ in the equation to find the pollution level y on the aforementioned date:
$y=7(1-\cos2\pi x)(x+10)+100e^{0.2x}$
$y=7[1-\cos2\pi (0)](0+10)+100e^{0.2\times0}$
$y=7(1-\cos 0)(10)+100e^{0}$
$y=7(1-1)(10)+100(1)$
$y=7(0)(10)+100(1)$
$y=0+100$
$y=100$
Therefore, the pollution level on January 1 of the base year is 100.