Sunday, January 25, 2015
Some folks express shock that agricultural chemicals can sometimes be found in groundwater, but nearly everything we use on the surface has the potential to get the wider environment, including into groundwater.
(Image: Tapwater. Credit: EPA.)
This isn't a big scare story. Most Hawaiian water is perfectly safe. Levels of all kinds of contaminants can be detected in the tiniest amounts, but almost all are far below levels of concern.
Man made materials get into the water. And lots of natural materials do, too. Like bacteria, which is a reason for chlorination.
Volcanic activity can contaminate groundwater with sulfur and other compounds.
“Some volcanic gases such as sulfur dioxide dissolve in groundwater, making the water acidic,” writes the US Geological Survey.
Arsenic is an odorless, tasteless and toxic element that can occur in groundwater. It can sometimes be the result of human activities, like insect treatment of wood, but in many parts of the world, arsenic is a natural contaminant, and a dangerous one.
Specific areas on every continent have natural arsenic contamination problems. And irrigating with arsenic-contaminated groundwater can transfer the toxicity to farmland, and then to crops. Arsenic-contaminated rice is a particular issue. Here’s an FDA report on arsenic in rice. Here’s an EPA resource on arsenic in groundwater.
Agricultural chemicals are a focus of concern, but they’re far from alone.
“Pesticides and fertilizers can find their way into groundwater supplies over time. Road salt, toxic substances from mining sites, and used motor oil also may seep into groundwater. In addition, it is possible for untreated waste from septic tanks and toxic chemicals from underground storage tanks and leaky landfills to contaminate groundwater,” says The Groundwater Foundation.
Pesticide contamination of groundwater has been a worrisome issue in Hawai`i, and there are specific areas of concern, but the Department of Health and the island water boards say almost all ground water in the Islands is safe to drink.
The Honolulu Board of Water Supply has issued statements about two chemicals, the herbicide bromacil and the termite killer dieldrin, which is no longer used. Both are found as contaminants in some O`ahu wells, but in levels below EPA levels of concern.
On the island of Kaua`i, most of the contaminants found in water are natural, the result of natural weathering of volcanic rocks. And in most Hawaiian water, they’re at lower levels than EPA established levels of concern.
Lead, copper and cadmium show up in Hawaiian water, apparently associated with corrosion of household plumbing. Each of those could cause significant threats to human health in high doses, but again, mostly, it’s found at low levels compared to the established “maximum contaminant level” or MCL.
You'd think that big things like plastics would be a threat to marine life, but pretty safe from being a groundwater contaminant. Maybe, but the sealants, linings and solvents associated with a lot of plastic products can end up in groundwater, too.
And in areas that have been extensively used for agriculture, some agricultural chemicals show up, also generally at levels significantly below the MCL concern level.
Several sites show levels of trichloropropane, a soil fumigant, and DCPA, an herbicide with the unpronounceable name dimethyl tetrachloroterephthalate.
On Kaua`i, you can check out the Water Department’s report on the results of testing for contaminants in water for the island’s various communities at this site. Here's Maui County. Here's Hawai`i County. And Honolulu County.
Some Hawaiian wells are contaminated with an industrial solvent and a contaminant in fumigation chemicals called 1,2,3-trichloropropane or TCP. It is denser than water and readily travels down to the groundwater. It is extremely persistent, having been banned in agricultural uses three decades ago. Most tests show that when present, its concentrations are within the guidelines.
The agricultural chemical atrazine, an herbicide, is also occasionally found in low levels in well water near current or former agricultural areas. While it is still used, its use has dropped significantly since the days of the sugar industry, from 400,000 pounds in 1964 to 77,000 pounds in 2012.
Unlike TCP, atrazine does not readily travel into groundwater, and more than 90 percent of community water systems in the Islands had no detectable levels, with the remaining systems having levels below the established levels of concern.
All that said, if you’re worried about contaminants in your drinking water, there is whole range of options for home filtration, from activated charcoal filters, to distillation, reverse osmosis and others. Here’s an Environmental Protection Agency handbook on home water treatment.
© Jan TenBruggencate 2015