Assessment of Uranium, Manganese, Fluoride, Nitrate, and Nitrite in Domestic Well Water in Maine, Michael Foley and Robert Marvinney

Transcription

1 Assessment of Uranium, Manganese, Fluoride, Nitrate, and Nitrite in Domestic Well Water in Maine, Michael Foley and Robert Marvinney 2011 Northeast Private Well Water Symposium November 14 & 15, 2011

2 In cooperation with From the Maine Center for Disease Control Andrew Smith, State Toxicologist Rebecca Lincoln, Environmental Health Specialist Funding: U.S. Department of Health and Human Services Centers for Disease Control and Prevention National Center for Environmental Health, Health Studies Branch Private Well Initiative for Environmental Surveillance and Public Health

3 Presentation outline Overview of private wells in Maine and quality concerns. Data used in this project USGS Study on Arsenic in Maine o Protocol for Data Preparation Uranium and geology o Geocoded data Results by analyte at the township level Summary and Conclusions.

4 Maine Private Wells 44% of Maine households rely on private wells for water a higher proportion than any other state Fewer than 40% of wells have been tested for arsenic, uranium, and other analytes Elevated levels of some contaminants: Arsenic: 10% > 10 ppb Uranium: 5% > 30 ppb Up to 1/3 of wells may have radon > 4000 pci/l Also high Manganese and Fluoride

5 Available Data Sources Test results from the state public health laboratory (Health and Environmental Testing Laboratory, HETL ) o ~3,000 tests per year Well characteristics data from Maine Geological Survey o Depth o Overburden thickness o Yield

6 USGS screening Protocol for Preparing Data o Used all well test data from (18,000+ results) o Developed protocol for de-duplication, cleaning, geocoding o Problems areas: Duplicate/erroneous records Public water supply data Multiple tests per source How to handle treated/filtered wells o Winnowed data set to 13,843 samples from 11,111 individual sources o For multiple tests: Use maximum value

7 Arsenic Results from 2010 USGS study Statewide 18% wells > 10 ppb; 4% > 50 ppb Several areas with high As identified Highest tested well was 3100 µg/l. Measures at town level: Maximum Median % above guideline Note: Self-selection bias the dataset Nielsen and others, 2010, USGS SIR

8 Uranium 238 Uranium is naturally occurring in rocks in Maine. Decay products include Radium and Radon Health effects of Uranium in groundwater: Potential to be both chemically and radiologically toxic Principal concern with ground water exposures are toxic effects on kidney Within kidneys, proximal tubules are the structures principally damaged by uranium. Consequences of tubular injury is decrease ability to reabsorb water and small molecules from urine Effects on kidney appear reversible Some evidence that chronic exposure associated with increase blood pressure Lifetime Cancer risk estimates of < 1 per 10,000 at levels around 30 ppb

9 Uranium Statewide 5% wells > 30 ppb. Two distinct areas of Maine identified as more likely to have high uranium levels Highest tested well was 3500 µg/l. Levels in 100 s not uncommon. Measures at town level: Maximum Median % above guideline Note: Self-selection bias the dataset

10 Maximum uranium concentration ppb Median uranium concentration ppb

11 Town Uranium - 20 highest maximum uranium concentrations (ppb) by town County Maximum (ppb) Median (ppb) Percent of samples > 30 ppb Total number of uranium samples per town Durham Androscoggin 3, Naples Cumberland 3, Sebago Cumberland 2, Falmouth Cumberland 1, Swanville Waldo 1, Bar Harbor Hancock 1, Gray Cumberland 1, Nobleboro Lincoln 1, Peru Oxford Greene Androscoggin Farmingdale Kennebec Bridgton Cumberland Limington York Lincoln Penobscot Poland Androscoggin Standish Cumberland Dedham Hancock Stonington Hancock Windham Cumberland Baldwin Cumberland

12 USGS analysis of U in rocks

13 Generalized Bedrock Geology Most of Maine is underlain with metamorphic rocks of numerous varieties Metamorphism is more intense in the southern part of the state. Granites and related igneous rocks intrude the metamorphic rocks and are more prevalent in the south and west.

14 Two-mica Granite Sebago granite. Late-stage intrusion. Large-ion elements are concentrated in the later crystallizing portions of the melt. Granites with both muscovite and biotite micas are characteristic of late-stage intrusions.

15 Geocoding sample locations While the USGS analysis of As was limited to town aggregation, we had access to street addresses in the HETL database. Of ~ 11,000 results in the database, ~ 8,000 had valid street addresses that could be geocoded. Used standard ArcGIS tools to assign XY locations for sample addresses. Allowed us to compare analyses with geology.

16 Uranium and Geology Point data overlays with geology. Strong concordance of wells with Uranium > 30 ppb and granitic intrusions.

17 A Caveat on Spatial Accuracy Geocoded addresses have a spatial accuracy based on street addressing schema ~ m. Geology from 1:500,000-scale compilation. Highly generalized. Positional accuracy of lines ~1,000 m or more! Contacts of intrusions may be better placed than contacts of thin metamorphic units.

18 Other Well Water Contaminants in Maine Manganese Fluoride Nitrates

19 Analyte # records used for analysis Maximum Contaminant Levels (MCL) Samples w/concentration levels equal to or greater than MCL value Number of samples Percent of total Manganese 12, ppm % Fluoride 11,964 2 ppm % Uranium 11, ppb % Nitrate 11, ppm % Nitrite 11,691 1 ppm 5 <0.1% Numerical Results: Number of samples that had concentration values equal to or greater than the Maximum Contaminant Level (MCL) for each analyte.

20 Spatial Results: Maps showing where concentrations of nitrate and nitrite exceed the MCL

21 Spatial Results: Maps showing where concentrations of F and Mn exceed the MCL

22 Summary & Conclusions Project has allowed us to summarize/map data on a wide range of contaminants -- Protocols can be used on additional datasets These data do not represent a random sample Subject to self-selection bias Allow us to identify hot spots and examine spatial variability Identification of hot spots and overlays with geology will allow us to: predict high-risk areas, target education, encourage testing,

23 Next Steps Access water quality data from private labs -- May have data in areas that are under-represented in the HETL data Geocode data for additional analytes for comparisons with detailed geology Cross-reference water quality data with well characteristics data