By Sally Brown, University of Washington

Abstracts of these resources are available in the searchable Information Portal offered to Northwest Biosolids members.

  1. Is House Dust the Missing Exposure Pathway for PBDEs? An Analysis of the Urban Fate and Human Exposure to PBDEs

  2. Persistence of Polybrominated Diphenyl Ethers in Agricultural Soils after Biosolids Applications

  3. Parabens. From environmental studies to human health

  4. Occurrence, temporal variation, and estrogenic burden of five parabens in sewage sludge collected across the United States

  5. Contact dermatitis from “Scotchgard”, a stain repellent for fabrics

Nick Basta can be a very funny guy.  Nick is a professor at THE Ohio State University and a soil chemist by training. He has worked with biosolids for decades.  I recently saw Nick at a Water Research Foundation research planning meeting in Denver.  As with all meetings or conversations relating to biosolids these days, the topic of PFAS came up.  Nick was right there: He related the story about a talk he had recently given.  When asked about PFAS- Nick pulled some Glide Dental Floss out of his pocket (a peer-reviewed study detected PFAS in the floss).  Amazed - he told the audience that despite the hazard, he had actually been allowed on a plane carrying this stuff!  As the discussion of contaminants continued the discussion turned to the antimicrobials, TCC and TCS.  Nick said in frustration ‘do you realize that we are talking about soap here’.  Hard to get too upset when you put things in the appropriate context.  And that is what the March library is about - putting these contaminants into context.  

The library this month is named ‘Cottage Industry’ to reflect the fact that the vast majority of ‘contaminants’ we are currently concerned about come not from belching factories but from peoples’ homes.  I’m not saying that there is no belching going on in those homes, it is just that domestic belching carries different connotations and stigmas than industrial belching.  For many decades those concerned about the land application of biosolids have pointed out that municipal wastewater accepts industrial discharges.  The focus had been on the great unknown of giant plants with giant pipes.  Another way to express this is to call them point sources.  Point source contamination is easy to identify and easy to regulate.  That is not the case for cottage industries or what comes out of your home.  What is easy to do in this case is to point out that if you are really worried about this stuff you should consider the risks posed by living in your house- not by the biosolids.  

The first four articles provide paired comparisons between home concentrations and biosolids concentrations of classes of compounds that were singled out in the recent EPA OIG report.  Nick has prepared a response to that report and will be presenting that response at Biofest (Sept 13-15 at Skamania outside of Portland).  It starts with an article quantifying human exposure to PBDEs (polybrominated diphenyl ethers) commonly used as flame retardants.  The authors centered their study in Toronto and considered a range of pathways of exposure.  They note that people in N America have about 20x the body burden as our European counterparts.  The majority of that comes from household dust.  Next biggest is eating meat and drinking milk.  If you breast feed – the most significant exposure to your infant throughout their life will be breast milk.  Searching that article for the terms ‘wastewater’ or ‘biosolids’ did not give any hits.  That is because biosolids are not a significant source of exposure to PBDEs.  The article has tables of measured PBDE concentrations in air, dust, soil, water, meat and dairy.

Here are the estimated daily intake sources (EDI):  The first graph shows uptake for an average Canadian and the second shows minimums and maximums.

est. daily intake (EDI)

The second article - all about PBDEs in biosolids is included for confirmation.  Here biosolids samples were collected over time – likely from Blue Plains in DC (a large mid- Atlantic WWTP that made lime stabilized biosolids at the time) and farms that had received no applications, one application or more than one application of the biosolids.  Average biosolids concentrations of a sum of types of PBDEs ranged from about 1-2 ppm.  One figure from the text pretty much sums up this paper.  The PBDEs were found in both the biosolids and control soils. In low ppb concentrations.  If you want exposure to PBDEs stay home and stop dusting.  Don’t even think about eating biosolids.

pbde concentration

From here we go to parabens.  You may not have any idea what parabens actually are - I didn’t.  It turns out that they’re preservatives that are commonly added to products like cosmetics to increase their shelf life.  They can also be added to pharmaceuticals and food.  The third article gives you a crash course in Parabens 101, including common home exposure.  They started being used in the 1920s and are found in 80% of all personal care products.  The authors estimate that daily home exposure is equivalent to 1.26-2.4 mg kg of body weight with the majority coming from cosmetics and other personal care products.  They also go into detail about how much is in your household dust.  Estimates for intake through breathing- a common activity in homes- is 0.55 ng kg body weight per day.

Below is their diagram for environmental pathways.  ‘Sludge’ makes it into the picture but with no clear pathway to the person.

paraben exposure

From here we go to paper #4 that details concentrations of these compounds in wastewater and biosolids.  Here is the graphical abstract from that paper:
paraben sewage sludge

You can look at it this way:  using an average body weight of 60 kg and assuming you breath 24 hours a day (G_d willing), your home exposure just from breathing is 33 ng per day.  Breathing at home for a week, not counting other routes of home exposure that are much higher than breathing, gives you the same exposure as eating a kg of biosolids.  I don’t know about you but I’d rather breath than eat a kg of biosolids.  And you know I love biosolids.  

Finally, we go to article #5.  This one is from 1963 and is about a guy who got a skin rash from wearing pants treated with Scotchgard.  A recent article (#6- doesn’t fit in the format for the library but happy to send) goes into detail about concentrations of side-chain fluorinated polymer surfactants also known as side- chain perfluorooctane sulfonamide-urethane polymer and side chain perfluorobutane sulfonamide-urethane polymer- also known as Scotchgard- in biosolids.  The authors sound the alarm noting that concentrations of these compounds are much higher than PFAS.  When everybody starts panicking about this new and even more terrifying version of perfluorinated compounds, stay calm.  Remember that Scotchgard has been giving people rashes for close to 60 years. Home exposure for these compounds - like the others in this library is sure to be orders of magnitude higher than in biosolids.