Narrative standards exist in Illinois Pollution Control Board (IPCB) regulations at 35 IAC 302.210 and in Subpart F for General Use Waters and at 302.540 and elsewhere in Subpart E for Lake Michigan Basin Waters. Lake Michigan Basin waters include all tributaries of Lake Michigan, harbors and open waters of the Illinois portion of the lake. General Use Waters cover all other waters of the state except those waters designated as Secondary Contact and Indigenous Aquatic Life Use Waters, which consist of several canals and rivers in the Chicago area. A narrative standard also exists for Secondary Contact Waters but derived criteria are not yet included in the list of criteria at this site.
The narrative standards allow the Illinois EPA to derive numeric water quality criteria values for any substance that does not already have a numeric standard in the IPCB regulations. These criteria serve to protect aquatic life, human health or wildlife, although wildlife based derived criteria have not yet been derived. The following list provides the criteria derived to date. The reader should pay particular attention to the "Notes for Table Headings" found below the list, because many criteria are provided with important comments. For example, some criteria have been derived from a less than ideal data set yet we include these values because we find it desirable to have some numeric indication of toxicity. These values may not be suitable for use in a regulatory setting, however. Criteria that have been used to limit discharges of a substance in an NPDES permit are published quarterly in the Illinois Register. All values on this list are subject to recalculation at any time. Illinois EPA will endeavor to keep this list updated. References to criteria in this list should include the date contained in the list heading.