Returns environmental indicator values and state percentiles for
block groups. Can filter to a specific indicator type or return all.
Args:
state: Two-letter US state abbreviation (e.g. 'WA', 'CA').
county_fips: Optional county FIPS code (3-digit or 5-digit).
If omitted, returns state-level results.
indicator: Optional specific indicator to focus on. Options:
'pm25', 'ozone', 'diesel', 'cancer', 'respiratory',
'traffic', 'lead', 'superfund', 'hazwaste',
'wastewater', 'rmp', 'ust'. If omitted, returns all.
limit: Maximum number of block groups to return (default 50, max 500).