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Clay County, South Dakota: environmental and disease records

Cancer mortality in Clay County is 163.8 deaths per 100,000 people per year against a U.S. rate of 143.2. Federal databases place 85 regulated facilities, sites and hazards inside the county, led by Rail grade crossing (38), NPDES wastewater discharge permit (15), Gas station (mapped facility) (13). EPA AirToxScreen estimates a lifetime cancer risk from outdoor air toxics of 20 in a million, driven mainly by formaldehyde.

Rates are age-adjusted per 100,000 people. A cancer signal is marked significant when the lower bound of its 95 percent confidence interval is above the U.S. rate. Facility counts use active federal records located inside the county boundary. Approximate county center: 42.9002, -96.9832.

How this county ranks in South Dakota

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Cancer deaths and new cases versus the United States

Source: NCI and CDC State Cancer Profiles, both sexes, all ages. Sorted by the ratio of the county rate to the U.S. rate.

Cancer rates for Clay County compared with the United States
Cancer	Measure	County rate	U.S. rate	Times U.S.	95% interval	Years
Bladder	New cases	23.2	18.7	1.24x	13.4 to 37.9	2019-2023
Melanoma of the skin	New cases	28.8	23.8	1.21x	17 to 45.8	2019-2023
All cancer	Deaths	163.8	143.2	1.14x	134.6 to 197.6	2020-2024
All cancer	New cases	471.8	453.4	1.04x	419.2 to 529.3	2019-2023
Lung & bronchus	Deaths	31.3	30.2	1.04x	19.7 to 47.6	2020-2024
Lung & bronchus	New cases	41.8	51.8	0.81x	27.8 to 60.6	2019-2023

Mortality measures versus the U.S. county median

Source: County Health Rankings, built from CDC National Vital Statistics System death records. The comparison value is the median of all U.S. counties.

Mortality measures for Clay County
Measure	County	U.S. median	Difference	Unit
Premature death	7,573.5	9,842.6	-23%	years of life lost before age 75 per 100,000
Life expectancy	77.2	75.3	+3%	years
Child mortality	n/a	59.8	n/a	deaths under age 18 per 100,000
Infant mortality	n/a	6.2	n/a	deaths under age 1 per 1,000 live births
Injury deaths	56.3	96.9	-42%	deaths per 100,000
Drug overdose deaths	n/a	28.6	n/a	deaths per 100,000

Air toxics and air quality

EPA AirToxScreen 2020

Lifetime cancer risk from outdoor air toxics: 20 in a million. EPA treats 100 in a million as the upper end of acceptable risk and 1 in a million as the goal.

Formaldehyde13.95 per million
Carbon Tetrachloride2.92 per million
Acetaldehyde1.15 per million
Benzene0.64 per million

EPA Air Quality Index 2025

Monitored on 351 days: 308 good, 2 unhealthy for sensitive groups or worse. Median AQI 34, peak 117.

Regulated facilities, sites and hazards by type

85 active records inside the county from EPA ECHO, TRI, Superfund, Brownfields, NPDES, EIA, FAA, FRA and corrections data.

Rail grade crossing38
NPDES wastewater discharge permit15
Gas station (mapped facility)13
Major air pollution source2
Air permit holder (minor source)2
Public airport2
Brownfield property2
Large greenhouse gas emitter2
Wastewater plant (mapped facility)2
EPA air quality monitor1
Commercial airport1
Auto repair or body shop (mapped facility)1
Dry cleaner (mapped facility)1
Large hazardous waste generator1
Small hazardous waste generator1
Oil-fired power plant1

Highest-severity records

The 25 records with the highest Envyrofax severity in the county, with the agency identifier to cite in a records request.

University Of South Dakota, Vermillion
Major air pollution source.
EPA FRS registry ID 110001676286 (U.S. EPA ECHO) Agency record
Severity 4.5
Spirit Mound, Vermillion
Oil-fired power plant.
Record ID 6092 (U.S. Energy Information Administration)
Severity 4.1
Vermillion, City Of, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110006692702 (U.S. EPA ECHO) Agency record
Severity 3.5
Basin Electric Power Cooperative Spirit Mound Stat, Vermillion
Major air pollution source.
EPA FRS registry ID 110007186106 (U.S. EPA ECHO) Agency record
Severity 3.5
Vermillion DOT
EPA air quality monitor.
Record ID 460270001 (U.S. EPA AirData)
Severity 3.2
Jolley Elementary School, Vermillion
Brownfield property.
EPA FRS registry ID 110071978710 (U.S. EPA Brownfields (ACRES)) Agency record
Severity 3
Clay County Court House, Vermillion
Brownfield property.
EPA FRS registry ID 110071980569 (U.S. EPA Brownfields (ACRES)) Agency record
Severity 3
Masaba Mining Equipment, Vermillion
Large hazardous waste generator.
EPA FRS registry ID 110037442693 (U.S. EPA ECHO) Agency record
Severity 3
Basin Electric Power Cooperative - Spirit Mound Station, Vermillion
Large greenhouse gas emitter.
EPA FRS registry ID 110025243948 (U.S. EPA ECHO) Agency record
Severity 2.5
Vermillion Sanitary Landfill, Vermillion
Large greenhouse gas emitter.
EPA FRS registry ID 110061012229 (U.S. EPA ECHO) Agency record
Severity 2.5
Wakonda, Town Of, Wakonda
NPDES wastewater discharge permit.
EPA FRS registry ID 110006692551 (U.S. EPA ECHO) Agency record
Severity 2.3
Lewis & Clark Rural Water System (Wtp), Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110043272972 (U.S. EPA ECHO) Agency record
Severity 2
Harold Davidson Fld, Vermillion
Commercial airport. O.
Record ID VMR (FAA / U.S. DOT)
Severity 2
University Cleaners & Formal Wear, Vermillion
Dry cleaner (mapped facility). Mapped facility presence only; no compliance or exposure measurements.
Record ID node/3052415993 (OpenStreetMap contributors) Agency record
Severity 2
Melvin D. Stiegelmeyer Water Treatment Plant
Wastewater plant (mapped facility). Mapped facility presence only; no compliance or exposure measurements.
Record ID way/299596582 (OpenStreetMap contributors) Agency record
Severity 2
Lewis & Clark Rural Water, Vermillion
Wastewater plant (mapped facility). Mapped facility presence only; no compliance or exposure measurements.
Record ID way/546197173 (OpenStreetMap contributors) Agency record
Severity 2
Clay Rural Water Service, Wakonda
NPDES wastewater discharge permit.
EPA FRS registry ID 110009790850 (U.S. EPA ECHO) Agency record
Severity 1.5
Walmart Supercenter #3734, Vermillion
Small hazardous waste generator.
EPA FRS registry ID 110022925058 (U.S. EPA ECHO) Agency record
Severity 1.5
City Of Vermillion Code Compliance Dept, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110028124107 (U.S. EPA ECHO) Agency record
Severity 1.5
New Ag Retail Facility, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110071277773 (U.S. EPA ECHO) Agency record
Severity 1.5
Site B Collector Well, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110071279389 (U.S. EPA ECHO) Agency record
Severity 1.5
Donnelly Addition, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110071324405 (U.S. EPA ECHO) Agency record
Severity 1.5
Bliss Pointe Addition - Phase I, Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110071324947 (U.S. EPA ECHO) Agency record
Severity 1.5
Vermillion, City Of (Biosolids), Vermillion
NPDES wastewater discharge permit.
EPA FRS registry ID 110071508635 (U.S. EPA ECHO) Agency record
Severity 1.5
Irene Water Storage Improvements, Irene
NPDES wastewater discharge permit.
EPA FRS registry ID 110071539144 (U.S. EPA ECHO) Agency record
Severity 1.5

Correctional facilities

Prisons, jails and corrections operations with an EPA facility record, and the drinking water and wastewater compliance attached to them.

No correctional facility with an EPA record is located in this county.

Discovery / public records

Records to request for Clay County

South Dakota state cancer registry
Cancer incidence counts by census tract or ZIP code, by cancer type and year (de-identified). Any cancer cluster inquiries or investigations in Clay County, and their findings.
South Dakota vital statistics office
Death certificate counts by cause of death and residence tract or ZIP code, and the years behind the mortality measures above.
South Dakota health department, environmental epidemiology
Health consultations or assessments by ATSDR or the state health department covering the county, and any exposure investigations.
South Dakota environmental agency and the U.S. EPA regional office
Compliance history, inspection reports, notices of violation, penalties and enforcement actions for each facility above, cited by EPA FRS registry ID.
South Dakota drinking water program
Violation notices, sampling results and sanitary surveys for the public water systems serving the county, including any system serving a correctional facility.
Department of corrections or county sheriff
Water testing, grievances and environmental health inspections for the correctional facilities listed above.

Each Envyrofax address report includes a printable records request worksheet with the custodian and the exact request wording per finding.

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