“It’s all over,” says Allison Dondzila of Cribley Drilling & Champion Water in Dexter. She figures the company finds dangerous levels of arsenic in the water of one out of twenty wells it drills, and it drills hundreds every year.

“It’s not that the situation is worsening,” says Leon Moore, director of the environmental health division of Washtenaw County’s public health department. “It’s that we’re doing more testing. We thought it was isolated to the northwest corner of the county ten years ago, and now we’re finding arsenic in isolated pockets throughout the county.”

The idea of arsenic poisoning is understandably terrifying. “Elevated levels of arsenic can cause bladder, lung, skin, and prostate cancer,” says Dondzila. “There are also neurological effects,” adds Moore, “for example, numbness in hands and other extremities as well as the face.” And let’s not forget increased risk of stroke.

As evidence of arsenic’s dangers mounted, in 2001 the US Environmental Protection Agency announced that it was cutting the amount allowed in public water supplies from fifty to ten parts per billion. Soon after, Washtenaw County lowered the amount permitted in private wells to match the federal standard. Moore explains the thinking behind the change: “People over 50 ppb will have a problem,” he says, “but at 10 ppb, you’d have to drink two liters a day for seventy years for it to have an effect.”

What’s a poison doing in well water in the first place? “Arsenic is a natural contaminant found in bedrock,” explains Moore. “We have a lot of iron in Washtenaw County, and arsenic is attracted to iron. We’ve also found that we’ve seen higher levels of arsenic in homes that have been vacant for a while.”

Moore’s department will test water samples for residents for $17. The tests are mandatory for all new homes and wells and when existing homes are sold or the deed is transferred. The department has tested about 8,000 homes since 2001. Only one-half of 1 percent exceeded the old standard of 50 ppb–but 9 percent had arsenic at 10 ppb or above.

Fortunately, there’s almost always a solution. “Arsenic only affects you when it’s consumed,” explains Dondzila. “So it’s really only water for drinking and cooking that’s a problem, not water for humidifiers or washing clothes or bathing. For arsenic below 50 ppb, usually an under-the-sink reverse osmosis treatment should do it. Above that, there’s whole house arsenic removal, where you put a large tank after water soften to remove the arsenic. And if your level’s really high, then there’s drilling a new well.” Another water table at the same location will often have lower arsenic levels–though the only way to know for sure is to drill and have a sample tested.

The solutions aren’t cheap. “The under-the-sink reverse osmosis units average $650 to $850 installed,” says Dondzila. “The whole house treatment averages $2,000 to $2,300 installed, and that includes the water test. The average 100-foot well costs between $4,500 and $5,000. That includes hooking up to the house but not upgrades like a bigger tank or pump or geothermal heating. All that’s more.”

But the success rate is high. “We’ve found with reverse osmosis devices a 92 percent removable rate,” says Moore. “And the other systems will remove 96 percent.” Either will lower arsenic levels from 50 ppb to less than 5 ppb.

Moore says there have been only a handful of cases where owners voluntarily tested their water, found elevated levels of arsenic, and elected not to treat their water. That’s risky but legal–until the deed to the property is transferred, county regulations can’t touch them. They can keep drinking that water as long as they live.

That’s not for Dondzila, who lives across the border in Livingston County. “I have arsenic in my water,” she says. “I have 36 ppb so I have reverse osmosis at my kitchen sink–and above that I have an osmosis removal filter. That brings it down to .001 ppb.”