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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality data for 22 cities serving 3,905,513 residents
Cook County in Illinois has an average water quality score of 78/100 (Grade B) based on analysis of 22 municipal water systems. The county's water systems serve approximately 3,905,513 residents.
Water quality in Cook County is fair, with some cities showing room for improvement. 7 cities have scores below 70, indicating elevated contaminant levels that residents should be aware of. Wheeling has the best water quality at 94/100.
22 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Wheeling Top concern: Fluoride (17.7% of limit) | 94 | A | 38,529 |
| 2 | Tinley Park Top concern: Total Trihalomethanes (21.4% of limit) | 93 | A | 52,279 |
| 3 | Calumet City Top concern: Fluoride (18.4% of limit) | 91 | A | 33,051 |
| 4 | Arlington Heights Top concern: Fluoride (18.6% of limit) | 89 | A- | 73,486 |
| 5 | Bartlett Top concern: Total Trihalomethanes (21.4% of limit) | 87 | A- | 38,963 |
| 6 | Schaumburg Top concern: Fluoride (18.6% of limit) | 86 | A- | 76,527 |
| 7 | Oak Lawn Top concern: Fluoride (24.6% of limit) | 86 | A- | 57,917 |
| 8 | Berwyn Top concern: Total Trihalomethanes (42.5% of limit) | 86 | A- | 50,288 |
| 9 | Park Ridge Top concern: Fluoride (18.3% of limit) | 86 | A- | 37,902 |
| 10 | Des Plaines Top concern: Fluoride (16.7% of limit) | 84 | B+ | 60,075 |
| 11 | Evanston Top concern: Fluoride (13.9% of limit) | 83 | B+ | 79,968 |
| 12 | Orland Park Top concern: Lead (28.7% of limit) | 83 | B+ | 55,957 |
| 13 | Chicago Top concern: Fluoride (18.3% of limit) | 82 | B+ | 2,741,897 |
| 14 | Glenview Top concern: Lead (36.4% of limit) | 81 | B+ | 50,302 |
| 15 | Cicero Top concern: Total Trihalomethanes (35.5% of limit) | 75 | B | 81,448 |
| 16 | Streamwood Top concern: Haloacetic Acids (41.6% of limit) | 69 | C+ | 44,115 |
| 17 | Skokie Top concern: Chromium (48.3% of limit) | 68 | C+ | 70,466 |
| 18 | Mount Prospect Top concern: Total Trihalomethanes (61.6% of limit) | 68 | C+ | 57,546 |
| 19 | Oak Park Top concern: Lead (33% of limit) | 67 | C+ | 50,008 |
| 20 | Hoffman Estates Top concern: Lead (47.5% of limit) | 65 | C+ | 47,459 |
| 21 | Palatine Top concern: Haloacetic Acids (58.5% of limit) | 53 | D | 66,114 |
| 22 | Hanover Park Top concern: Total Trihalomethanes (70.2% of limit) | 47 | F | 41,216 |
Top detected contaminants across county water systems
| Contaminant | Avg Level | Max Level | EPA Limit | % of Limit | Cities |
|---|---|---|---|---|---|
| Total Trihalomethanes | 19.777 ug/L | 56.149 ug/L | 80 ug/L | 24.7% | 22 |
| Haloacetic Acids | 13.524 ug/L | 35.081 ug/L | 60 ug/L | 22.5% | 19 |
| Lead | 0.003 mg/L | 0.007 mg/L | 0.015 mg/L | 21.6% | 19 |
| Fluoride | 0.846 mg/L | 1.423 mg/L | 4 mg/L | 21.2% | 20 |
| Mercury | 0 mg/L | 0.001 mg/L | 0.002 mg/L | 18.1% | 21 |
| Copper | 0.221 mg/L | 0.747 mg/L | 1.3 mg/L | 17% | 22 |
| Arsenic | 0.002 mg/L | 0.005 mg/L | 0.01 mg/L | 16.7% | 19 |
| Nitrite | 0.165 mg/L | 0.36 mg/L | 1 mg/L | 16.5% | 19 |
Recent violations across county water systems
Showing 10 of 20 recent violations
Water quality in Cook County, Illinois reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 22 municipal water systems serving a combined population of over 3,905,513 residents.
The county shows moderate water quality performance, with scores ranging from 47/100 in Hanover Park to 94/100 in Wheeling. This 47-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across Cook County water systems include Total Trihalomethanes, Haloacetic Acids, Lead. All monitored contaminants remain within acceptable levels relative to EPA Maximum Contaminant Levels (MCLs).
Water quality in Cook County is fair but shows room for improvement. Residents in cities scoring below 70 should consider water filtration, particularly for drinking and cooking. Check your specific city's report above for personalized recommendations.
Cook County has an average water quality score of 78/100 (Grade B) based on analysis of 22 municipal water systems serving 3,905,513 residents.
Wheeling has the highest water quality score in Cook County at 94/100. View the detailed report for Wheeling.
Given the water quality variation across Cook County, we recommend reviewing your specific city's water quality report. 7 cities have scores below 70, where filtration is particularly recommended.
Click on any city in the rankings table above to view its detailed water quality report, including contaminant levels, EPA compliance history, and filter recommendations.