solvents

Solving the Solvent Problem: Part 2 of a 2-Part Series

by Walter Mugdan

In Part 1, I explained that a large variety of chemical solvents were concocted over the past two centuries.  They are integral to nearly every industrial enterprise, but many of them are dangerous to your health if you ingest or inhale them.  Among the most common is PCE or “perc,” which is a probable human carcinogen.  The most common use of perc is as dry cleaning fluid.  In the past, many dry cleaners simply dumped their used perc on the ground, contaminating both soil and groundwater.   EPA’s “Superfund” list of the worst toxic waste sites in the country is littered with former dry cleaning facilities.

One of these Superfund sites is located in Nassau County, just a stone’s throw from where I live in Queens County.  I’m in the Little Neck part of Queens; and the former Stanton Cleaners sites is a half mile away in Great Neck.  When Stanton dumped its used perc down the drain, it contaminated the groundwater below.  This is bad enough under any circumstances, but here it was particularly dangerous, because Stanton was only about 300 yards away from a Great Neck drinking water supply well. To make matters even worse, perc vapors from the contaminated groundwater were getting into nearby homes and a synagogue.

The Stanton site was added to the Superfund list in 1999 and EPA installed a “pump-and-treat” system.  This is one of the ways that we use to solve our solvent problems.  Contaminated groundwater is pumped up to a small building at the back of the dry cleaner’s parking lot. There it’s treated to strip away the perc, and returned clean to the ground. More than 200 million gallons have been treated to date at the Stanton site.

As a precaution, a treatment system was also installed at the drinking water well; and vapors are now vacuumed from the soil before they can reach homes and other buildings. (The current dry cleaning operation – a different company, though still using the Stanton name – has state-of-the-art equipment to prevent perc from entering the ground.)

Over the past three decades, we’ve developed a variety of techniques for solving solvents problems.  In a “pump-and-treat” approach like the one used at Stanton, the contaminated groundwater is cleaned by passing it through a carbon filter or an air stripper (in which air is blown through tiny water droplets, stripping away the contaminants).  Alternatively, various in situ techniques can be used to clean the groundwater in place.  Other chemicals that react with the solvents to form harmless substances can be added to the groundwater; or nutrients can be added to stimulate microbes that degrade the solvents. More

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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Solving the Solvent Problem: Part 1 of a 2-Part Series

by Walter Mugdan

If you’re like me, you’re interested in the etymology of words.  My job at the U.S. EPA involves cleaning up toxic waste sites.  Lots of the words used in my business are scientific and derive from Latin or Greek (neither of which I studied in school).

The chemistry term “solvent” comes from the Latin solvere, meaning to loosen or untie.  The same Latin root gives us other words – words that have both scientific and common meanings.  We solve problems, both mathematical and human … or at least we search for the solutions to those problems, assuming optimistically that they are in fact soluble.  The Declaration of Independence explains why we chose to dissolve the political bands which tied us to England.

In the scientific context, a solvent is a substance (typically a liquid, but not necessarily) that dissolves another substance, called a solute; the result is called a solution.  Life as we know it would not exist if nature had not made possible this chemistry trick.  The most common solvent on earth is water.  The world’s oceans, from which life arose, constitute a solution with thousands of solutes, many of them essential to life.  The most obvious is sodium chloride – salt – the primary ingredient of salt water.  More mundane water solutions are all around us, including virtually any flavored drink from coffee to lemonade to Gatorade to whiskey.

Today there are a zillion other solvents out there, and they are used in nearly every industry from the simplest to the most complex.  Some, like turpentine (distilled from the sap of pine trees) have been in use since ancient times.  But most have been concocted in the 250 years since the start of the Industrial Revolution.  From paint thinners to cleaning agents to manufacturing intermediates, solvents are ubiquitous in the industrial world.

Why is this relevant in an environmental blog?  And why does the title of this blog suggest that there is a solvent problem to which we need a solution?  Here’s why: like everything else in the industrial world, the use of solvents creates wastes; and until pretty recently those wastes have been poured, leaked, spilled, pumped and dumped onto the ground and into the water.  What’s more, nearly all of these solvents are bad for you, some extremely so.

Two of the most common are trichloroethylene (TCE) and tetrachloroethylene, also known as perchloroethylene, PCE or “perc.”  TCE is used in a wide variety of industries, from extraction of vegetable oils to medical anesthesia, but it is most commonly used as a degreaser and cleaner for metals and electronics.  TCE was almost certainly used in making every iPod or iPhone or iPad you own (or covet).

Perc is most commonly used as dry cleaning fluid — it’s what provides that distinctive smell when you bring your clothes home from the cleaner.

Both TCE and perc are probable human carcinogens, and one or both are found well over half of the sites on the U.S. EPA’s Superfund list of the worst toxic waste sites in the country.   That list is littered with former dry cleaning establishments, many of which simply poured their used perc into the ground.   Here in the Big Apple there are literally hundreds of dry cleaners.  While most of them have not contaminated the soil and groundwater, if you’re reading this blog you’re probably not too far from a site where a dry cleaner has done just that.

Watch for Part 2 of this series, where we’ll consider how we can solve the solvents problem.

About the Author: Since 2008 Walter has served as Superfund director for U.S. EPA Region 2, managing the region’s toxic waste cleanup, emergency response and brownfields programs.  For the previous six years he was director of the region’s air, water, hazardous waste and environmental review programs.  He joined Region 2 in 1975 as a staff attorney doing air pollution enforcement work.  From 1991 to 2002 he held various supervisory positions in the region’s legal office, culminating as Regional Counsel.  In his private life he heads a small, local conservation group in northeast Queens.  He enjoys bicycling, kayaking and hiking; and since 2010 he has been moonlighting as an Executive Producer (read: source of funding) for his daughter’s nascent career as an independent film maker.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.