
<tr class="even">
<td align="left">state</td>
<td align="left">state</td>
<td align="left">keyword</td>
</tr>
<tr class="odd">
<td align="left">city</td>
<td align="left">city</td>
<td align="left">keyword</td>
</tr>
<tr class="even">
<td align="left">station</td>
<td align="left">station</td>
<td align="left">keyword</td>
</tr>
<tr class="odd">
<td align="left">last_update</td>
<td align="left">last_update</td>
<td align="left">date</td>
</tr>
<tr class="even">
<td align="left">pollutant_id</td>
<td align