Please click on the following link to access EPA AQS Web Tool:
https://www.epa.gov/outdoor-air-quality-data
The following instructions will help you download the Lead monitoring data for Clark County, NV:
Select “Pb” in the Pollutant drop box
Once Pb is selected, the YEAR drop box will be activated
Select a year in the “Year” drop box
Once a year is selected, the GEOGRAPHIC AREA drop box will be activated 

There are 3 choices to select a geographic area:

• “Select a State” – select Nevada
• Or “Select a City” – select Las Vegas-Paradise, NV
• Or “Select a County” – select NV-Clark

Once a geographic area is selected, the last drop box, MONITORING SITE will be activated
There is only one monitoring station that measures Lead in Clark County: 320030540
One can include or exclude Exceptional Events, in the case of Lead either selection is fine.
Click Get Data
The data will be retrieved and after a few moments, a data link is displayed.
Click on Download CSV (spreadsheet) to download the data
This file is in an excel format

Although the instruction above are specific to Lead, any criteria pollutant, any year, any geographic area in the US and any monitoring site in the US can be downloaded.