If a forest fire is serious it can be seen from miles away. Perhaps when none is seen there is no serious fire there at all.
This abstract does not mention what constitutes an “unsafe level”. Presumably this would be the drinking water MCL of 10 mg/L but perhaps the “safe” level is higher than the MCL. Like most studies of this type the presumption is that there must be a problem we just have not looked close enough.
Blake SB. Spatial relationships among dairy farms, drinking water quality, and maternal-child health outcomes in the San Joaquin Valley. Public Health Nurs. 2014 Nov-Dec;31(6):492-9. doi: 10.1111/phn.12166.
OBJECTIVE: Access to clean and affordable water is a significant public health issue globally, in the United States, and in California where land is heavily used for agriculture and dairy operations. The purpose of this study was to explore the geographic relationships among dairy farms, nitrate levels in drinking water, low birth weight, and socioeconomic data at the ZIP code level in the San Joaquin Valley.
DESIGN AND SAMPLE: This ecological study used a Geographic Information System (GIS) to explore and analyze secondary data.
MEASURES: A total of 211 ZIP codes were analyzed using spatial autocorrelation and regression analysis methods in ArcGIS version 10.1.
RESULTS: ZIP codes with dairies had a higher percentage of Hispanic births (p = .001). Spatial statistics revealed that ZIP codes with more dairy farms and a higher dairy cow density had higher levels of nitrate contamination. No correlation was detected between LBW and unsafe nitrate levels at the ZIP code level.
CONCLUSION: Further research examining communities that use private and small community wells in the San Joaquin Valley should be conducted. Birth data from smaller geographic areas should be used to continue exploring the relationship between birth outcomes and nitrate contamination in drinking water.