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The Green Room: The Ann Arbor Area's 1,4 Dioxane Plume-Part24

As concern rises and detection methods improve, 1,4-Dioxane is being discovered in water sources across the country. Central to formulating remediation plans is determination of the safe level of exposure to this probable human carcinogen. What constitutes a true hazard as opposed to an “acceptable risk?”  Barbara Lucas goes in search of the answer in this 24th installment in our series on the Ann Arbor area’s 1.4 Dioxane Plume in “The Green Room.” 

David Fair:  This is 89-1 WEMU and I’m David Fair. Containment of Ann Arbor’s dioxane plume is the current goal. But right now, there are potential routes of low-level exposure.  Well water serving seven homes west of town have tested positive for dioxane. Earlier this week, more was discovered in the shallow groundwater beneath some homes in the city. In both instances, the concentrations are far below Michigan’s advisory levels.  In this 24th installment in our “Green Room” series, Barbara Lucas explores the question of what is a safe advisory level.

Andrew Maynard, from “Risk Bites” video:  How dangerous is the chemical 1,4-Dioxane….

Barbara Lucas (BL):  0.35 parts per billion dioxane in drinking water is the level determined by the  EPA to be a one in a million cancer risk, while 3.5 is a one in a hundred thousand risk. 

Andrew Maynard, from “Risk Bites” video:  Just being able to put a number on something bad happening brings up more challenging questions, including what you do with that number once you have it.  Who decides how much risk is OK…

BL: I’m watching a video from the “Risk Bites” series created by Dr. Andrew Maynard, the former director of the University of Michigan Risk Science Center. A growing number of states and cities are choosing to use the EPA’s 0.35 level as their guideline.  Meanwhile, Michigan’s proposed 7.2 safe level is over twenty times higher.  Why the discrepancy?  Could money and resources factor in?   While Michigan struggles to adjust its safe level of dioxane in drinking water from 85 to 7.2 ppb, people in Colorado are arguing over numbers under 1 ppb. 

Bonnie Rader: …and the others are trying to treat down to .35.  But the city of Denver and Waste Management have said that because they don’t believe the labs can get down to that number, they are insisting that the level for the Lowery landfill be .9.

BL: That’s Bonnie Rader. She’s a clean water activist in Colorado. Rader says numerous landfills in her state are leaching dioxane and facing groundwater cleanups. 

Rader:  I think regulators are just overwhelmed with how they’re going to do it.

BL: Eastham, Massachusetts on Cape Cod also has a landfill leaching dioxane.  The Massachusetts safe level is even lower than Colorado’s:  .3.  They’re delivering bottled water to 40 households until a municipal water system can be built.  Here’s Eastham Health Agent Jane Crowley.

Crowley: Our interest in protecting public health and the environment is to be as conservative and proactive as possible.

BL:  She says their local elementary school is on bottled water even though the tap water tests at a level below .3 ppb.

Crowley:  The elementary school, Eastham Elementary School, is down-gradient from the landfill.  We did go in—it was never in exceedance over that 0.3 level, but there was a detection.  It was above the reportable limit, but below the .3.  Proactively, we thought it was best to completely eliminate any possible consumption of any quantity.  So we immediately contracted to bring in bottled water.

BL:  Tucson Arizona is removing dioxane from their drinking water to below .1 ppb.  Jeff Biggs is Tucson Water administrator.  He says Tucson is guessing the EPA will someday regulate dioxane to .35, and they want to be proactive.

Biggs:  Eventually, health advisories turn into “Maximum Contaminant Levels” which are actually enforceable.  Advisories aren’t enforceable.   But Tucson water takes them seriously because we are here to protect the public.

BL:  Meanwhile, in Michigan, the EPA found eight municipal water systems serving water above .35.   Could what is deemed to be economically feasible affect what advisory level is followed? Note that in Tucson, the United States Air Force is responsible for the pollution. It is paying for Tucson’s treatment plant and the annual costs for operations.  In Ann Arbor, who’s paying for what is a constant challenge.  

Maynard:  Hello.  Andrew Maynard.

BL:  Andrew Maynard is a Risk Science expert. Formerly he was director of the University of Michigan Risk Science Center.  He’s currently Director of the Arizona State University Risk Innovation Lab.   

Maynard: Just looking at the politics around dioxane in Ann Arbor one factor is the shear cost of cleanup. So you've got economics coming into this, decisions being made trying to balance the cost of cleaning up with the potential impact on health. And in between the two you have science that's not 100% clear so both sides can argue things according to what they want to achieve.

BL: Compared to the statistically much greater risks we face on a daily basis, like the potential of a traffic fatality, the fears of dioxane might seem overblown.

Maynard:  As soon as people see the amount of money that it would take to get the risk down to a certain level they start looking at it and asking whether we actually want to do this. And that's when this question comes in maybe somebody is over-blowing the risks.

BL:  But, tell that to a family whose water contains a chemical that has even a remote chance of giving them cancer. In Washtenaw County, seven drinking water wells in current use have tested from 1 to 3 ppb.  How many more might have below 1 ppb, we don’t know, because the tests used don’t tell us. 

BL:   What does a dioxane testing procedure look like?  I’m at Ann Arbor Technical Services, on Wagner Road.  Phil Simon is the owner.

Phil Simon:  This year a lot of residential property sales have had a contingency requiring 1,4-dioxane and lead analysis. 

BL: Michigan real estate law doesn’t specify dioxane tests, but it does require disclosure of any known environmental hazards.

Simon:  We get a lot of panicked homeowners saying, “I’m closing in two days, can you please…”

BL:  My house is on municipal water, which the City of Ann Arbor regularly tests for dioxane.  At sensitivities all the way down to .07 pbb, it’s always been “non-detect.”  Simon’s lab is analyzing a sample of water I’ve brought from my house, as a demo.  When the 45 minute process is done, the verdict:

Simon: It’s less than .3 ppb, which is our method of detection limit.

BL:  Would you say with total confidence there is absolutely no—absolutely zero— dioxane in that water?

Simon:  We would say with total confidence that there is absolutely no dioxane to 0.3 micrograms per liter.  Below that, we can’t tell you.

BL:  He says they don’t report levels below 1 ppb because Michigan’s legal limit doesn’t go anywhere near that.

Simon:  We always implement methods that are sensitive enough to provide statistically highly confident data, to address the existing rules.  So if the State of Michigan wanted to push the reporting levels down below 1 ppb, and came to us and said, “We want to go to .5 or .1,” then we would work on pushing the method down.

BL:  But Massachusetts tests lower.  They put the Eastham elementary school on bottled water, even though their level was below .3 ppb.  Is Eastham overreacting?  Could knowing water has minute amounts of dioxane be a case of “too much information”?  The answer seems to depend on whom you ask. In Ann Arbor, and the State of Michigan, it continues to be an unanswered question.

Barbara Lucas, 89 One, WEMU.


“Dioxane discovered in shallow groundwater at Ann Arbor neighborhood park.” Ryan Stanton, MLive, October 18, 2016

Eastham Massachusetts Landfill

Lowry Landfill, Aurora, Colorado

City of Tucson 1,4-Dioxane Pamphlet 2012

Ann Arbor Technical Services

EPA Unregulated Contaminant Monitoring Rule (UCMR3)

EPA Technical Fact Sheet 1,4-Dioxane

Risk Bites Video on 1,4-Dioxane by Dr. Andrew Maynard

Washtenaw County Public Health Fact Sheet on 1,4-Dioxane

Michigan Real Estate Disclosure Law:

Barbara received a master's degree in Environmental Policy from the University of Michigan. She began her association with WEMU in 2003 as an intern with Washtenaw County, assisting with the weekly "Issues of the Environment" show. In 2003 she also began working in documentary film, and later established her own video production company.