Down the Drain, then Down the Hatch

John BalbusCal Baier-Anderson, Ph.D., is a Health Scientist.

Can nanoparticles get into our drinking water and if so, what’s the harm?

Nanoparticles are being used in cosmetics and other personal care products with increasing frequency.  Carbon fullerenes, also known as buckyballs, have recently been touted as imparting age-defying antioxidant benefits when added to skin cream.  And there are some studies that seem to support these claims.  But even if such claimed benefits turn out to be true, this is by no means the end of the story. 

Skin creams are eventually washed off and down the drain.  Once they enter a sewage treatment system, the fate of nanoparticles is largely unknown.  Depending on their physical and chemical properties, engineered nanoparticles may wind up in the sludge – the solids – or they could spill over into the wastewater discharge, and wind up in lakes, rivers and streams.  If the latter occurs, they could end up in our drinking water.

This is not wild speculation.  One of the most hotly debated issues in environmental science is the frequent detection of chemicals from pharmaceuticals and personal care products in our drinking water.

If fullerenes act as antioxidants, then what’s the big deal if they get into our drinking water — wouldn’t they be beneficial? The very properties that allow antioxidants to scavenge the reactive oxygen species (ROS) that can damage cells also allow these compounds to liberate them, by cycling between uptake and release.  Under certain circumstances, antioxidants are more likely to release ROS than to take them up.  More research is needed to understand under what conditions so-called antioxidants might be likely to contribute to rather than prevent cell damage.

A new study published in Environmental Health Perspectives evaluated the effect of a single oral dose of fullerenes and single-walled carbon nanotubes (SWCNTs) on the extent of oxidative damage to DNA in the liver, colon and lungs of rats.  The authors were duplicating a study that demonstrated oxidative DNA damage in these organs following a single oral dose of the constituents in diesel exhaust.  DNA damage is important, because it is often a precursor to cancer.

In the new study, rats fed either fullerenes or SWCNTs exhibited increased levels of DNA damage in the liver and lungs, sometimes even at quite a low dose.  Neither nanoparticle had a significant effect on the colon at the doses tested, however.

So what does all this mean?  In my view, since we already know that chemicals in personal care products can wind up in drinking water, we should take more of a look-before-we-leap approach to evaluating new chemicals, including engineered nanomaterials, for use in these products.  This need also extends, of course, to the thousands of ingredients already present in personal care products that have not been adequately tested for safety.

Among the questions we need answered up front:  what is the expected fate and transport of such nanoparticles in the environment, who or what might be exposed during this process (including fish, bacteria, and any other critters), and if they wind up in our drinking water, what are the potential health effects?  The study discussed in this post is but one tiny piece of this puzzle.  (Of course, oral exposure to nanoparticles may occur through routes other than drinking water contamination, such as through direct ingestion of nanomaterials in foods or via the mucociliary escalator that removes inhaled particles from the lung to the digestive tract.)

Clearly we need regulators to be asking more of these questions – and requiring companies to provide the answers.  As my colleague Richard Denison pointed out in two of his recent posts, however, this doesn’t appear to be happening with new chemical notifications being processed by EPA.  Instead, EPA seems to regard an absence of data as grounds for concluding an absence of risk.  And EPA gives the potential impacts at the downstream end of nanomaterials’ lifecycles very short shrift.

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