DECEMBER 2018 RESEARCH UPDATE

To view the article abstracts from this months research update follow this link: NOVEMBER 2018 RESEARCH UPDATE

Lists? Checking it Twice!

Holidays are a time of making lists.  I have many lists:  my holiday cards lists, menu lists, gift lists and so on and so forth.  Some believe that Santa makes a list of whose naughty and nice.

EPA has apparently tried to get into the spirit of lists his year too.  They just released a list of 352 pollutants identified in biosolids.  They tried to ape Santa with the naughty or nice designation but concluded that a lack of data or risk assessment tools precluded them from assigning these pollutants to their appropriate categories.  Thanks a lot EPA. For me, that puts you in the Scrooge category.  This month’s library, the last library of 2018, takes a quick look at that EPA list.

The first item in the library is the actual EPA document.  As the document correctly points out, the 503 risk assessment process was science based.  It also stressed the need to reevaluate the regulation periodically based on new information.  EPA does not have the staff to do this in a very thorough fashion, and multiple decades of land application with no appreciable hazard and a lack of public outcry had placed this on the back burner.  This report was actually written by the Office of the Inspector General (OIG) of the EPA and provided to the EPA Office of Water.

For this library I have cherry picked some of the contaminants discussed in the OIG report.  While the summary calls out pharmaceuticals, steroids and flame retardants, those have been dealt with in depth in previous libraries.  Of the 352 pollutants, the report calls out 61 that are not only not contained in shampoo, but are “acutely hazardous, hazardous or priority pollutants in other programs.”  Here it appears that the consultants who wrote the report culled pollutants from other people’s lists.  This included RCRA, the Priority pollutant list and the NIOSH hazardous drugs list (Table C1).  In the RCRA list, compounds are either labeled with a ‘U’ or a ‘P’.  U stands for toxic and P stands for acutely hazardous.  The ‘P’ compounds are the focus of the next 4 articles in the library.

First it is important to note that these lists are typically made outside of a realistic context.  The 503s considered concentrations in biosolids, pathways of exposure, and potential for risk based on actual use of biosolids in a real world context. The lists used by OIG have been generated without a consideration of use of biosolids and potential for exposure.  If a compound has been detected in biosolids and has appeared on one of these lists, in the view of the OIG authors that is sufficient reason for it to rate inclusion.  That may suggest it is worth looking into in greater detail,  but it in no way means that its presence in biosolids puts biosolids use in the naughty category.

The first compound is dimethoate.  Wikipedia is a great way to find out what dimethoate actually is.  It is an organophosphate insecticide that was developed in the 1950s.  In other words, it has been in use for decades.  Wikipedia says that it is readily taken up by plants and distributed throughout plant tissues.  The first article in the library was one of the only ones that I could find on this insecticide and biosolids (I even searched for dimethoate and sewage sludge).  The authors sprayed the compound at 0.47 L acre-1 on broccoli and tested soils and runoff and infiltration water for traces of the compound.  They tested this with soil amended with biosolids, yard waste compost and bare soil.  The half-life of the insecticide was less than 14 days on the broccoli and ranged from 31 ng g on the biosolids to 135 ng g on the bare soil.  It fell below detection on the soil amended with compost or biosolids within 5 days after spraying and within 8 days on the control.  Biosolids also reduced runoff potential of the compound with no differences seen in water that had infiltrated into the soil.  In other words, the takeaway for EPA OIG could be to ban it on the broccoli.

The second compound with a ‘P’ is N- nitrosodimethylamine (NDMA).  Again, we turn to Wikipedia (may want to think about adding Wikipedia to your donation list this year).  NDMA is a waste product of multiple processes and can be found in trace concentrations in certain foodstuffs (bacon and smoked meats).  It is likely carcinogenic and is used to make rats get cancer for research.  It can be generated during wastewater treatment when chlorine is added to effluent prior to release.  It falls under the broad category of nitrosamines.  The third article in the library used archived biosolids from a prior sewage sludge survey and tested them for the presence of these compounds.  The study tested biosolids from a total of 74 treatment plants.  NDMA was detected in 3% of the samples tested at a mean concentration of 504 ± 417 ng/g (ppb).  That translates into it was likely found in one sample at a high level and above detection in two others, not found in the 71 other samples tested.  Perhaps this high level could be attributed to an industrial source.  It is also not clear that there would be a potential for the presence of this compound in 3% of the tested biosolids to result in any risk based on likely end uses of biosolids.  Reported uses of this compound suggest that its presence in drinking water is likely a much more significant concern than concentrations in biosolids.  In other words, cross this guy off the list too.

From here we go to beryllium (Be), an alkali earth metal, the same column on the periodic table as calcium and magnesium.  Wikipedia says that Be is a rare element that is a component of traditional Christmas gifts such as emeralds and aquamarine.  It can be added to metals such as aluminum and copper to improve their physical properties.  It is used for aerospace applications as well as for x-ray equipment.  The 4th article in the library is from Sweden.  It reports testing results for a range of elements (including Be) in biosolids, animal manures and fertilizers.  The report starts with a statement about how strict environmental policies are in Sweden and how tough their limits are.  For the biosolids sampled, Be was below detection for just about all of them (46 out of 48) with a reported value of < 0.6 mg kg.  In contrast it measured 5 mg kg in manures (n=12) and 0.2-2.3 mg kg in fertilizers (n=4).  I don’t think that I need to add anything more on that one.

Finally, we go to chloroaniline 4 (4 -CA) and article #5.  This compound is used for production of pesticides and drugs.  It is a precursor of the antimicrobial compound chlorhexidine.  The article that I found here focuses on the fate of two antimicrobial compounds, triclosan (TCS) and triclocarban (TCC) in soil columns +/- biosolids applied on the surface.  In addition to looking at parent compounds, the authors also looked for degradation products of both compounds.  They detected chloroaniline and suggest that it was formed from the hydrolysis of TCC.  They also noted that it leached through the soil column.  It was detected in the leachate as a minor metabolite of the compound itself and only in low concentrations for a fraction of the periods sampled.  Metabolites and breakdown products of compounds can be more toxic than the parent compound.  DDE, a by- product of DDT mineralization, is a classic example of this.  While 4-CA was detected here, it was detected only fleetingly and it does not seem to be a major by -product of TCC decomposition.  It’s ability to move through soil to groundwater is a concern and this may merit additional study.  Here I would point out that the thorough risk assessment done on both TCS and TCC by George O’Connor at the University of Florida would likely have noted toxicities associated with the use of the parent compounds.

When you make your holiday lists- I would disregard this one from EPA.  Happy New Year and see you in February. 

Sally Brown, University of Washington