Wednesday, March 02, 2011

Pandemics & The Law Of Unintended Consequences

 

 

 

# 5348

 

A variation today on a theme we’ve touched on before.

 

What happens to the environment during a pandemic when large numbers of people in a community are taking – and subsequently excreting in their urine & feces – antivirals and antibiotics?

 

Many of the life-saving drugs used during a pandemic are excreted at some percentage from the human body unchanged or as a bioactive metabolite.  Tamiflu, Erythromycin, and Moxifloxacin are almost 100% bio-actively intact at excretion.

 

image

Supplemental Table 4. Assessing the Ecotoxicologic Hazards of a Pandemic Influenza Medical Response. Environ Health Perspect :-. doi:10.1289/ehp.1002757

 

 

A little more than four years ago, the subject of what happens to Tamiflu once it is excreted by the human body first graced these pages.

 

The blog was called The Law of Unintended Consequences, and it looked a study conducted at the Centre for Ecology and Hydrology in Oxford, England.

 

Their findings were released in the January 2007 issue of Environmental Health Perspectives (EHP) in a report entitled, Potential Risks Associated with the Proposed Widespread Use of Tamiflu, that illustrated what might happen if millions of people simultaneously began taking Tamiflu and releasing it into our environment.

 

The upshot of the the study was that scientists believed enough of the metabolite OC (oseltamivir carboxylate) would be present in some rivers and streams, after sewage plant processing, to present a genuine risk to the environment.

 

The concern being that enough Tamiflu might persist after wastewater treatment and release to rivers and streams that it might speed the development of resistant influenza viruses in waterfowl.

 

Fast forward to October of 2009 and we saw another report (see Everything Old Is News Again), based on studies done the previous year in Kyoto, Japan – that showed elevated levels of the OC Metabolite in wastewater discharge. 

 

More recently, investigators looking at the levels chemicals in rivers downstream from a pharmaceutical manufacturing hub in India, found staggering amounts of antibiotics along with signs of resistant bacteria. 


That story was recently well covered by Maryn McKenna on her Superbug Blog (see Drug residues and drug resistance in water: Not good).

 

Today, a new study appears in Environmental Health Perspectives that reports on another potential problem inherent in the massive distribution and consumption of antibiotics and antivirals during a pandemic.

 

WWTPs (Wastewater Treatment Plants) depend upon microbial activity in order to breakdown or `digest’ sewage.

 

Antibiotics in the sewage – at elevated levels such as might be seen during a pandemic – could inhibit microbial activity, resulting in the failure of WWTPs and the discharge of under-treated wastewater into the environment.

 

First a link to the study, an excerpt from the abstract, and a link to the press release . . . then I’ll return with a little more.

 

Assessing the Ecotoxicologic Hazards of a Pandemic Influenza Medical Response

Andrew C. Singer, Vittoria Colizza, Heike Schmitt, Johanna Andrews, Duygu Balcan, Wei E. Huang, Virginie D. J. Keller, Alessandro Vespignani, Richard J. Williams

Background: The global public health community has closely monitored the unfolding of the 2009 H1N1 influenza pandemic to best mitigate its impact on society. However, little attention has been given to the impact of this response on the environment.

 

Antivirals and antibiotics prescribed to treat influenza are excreted into wastewater in a biologically-active form, which presents a new and potentially significant ecotoxicologic challenge to microorganisms responsible for wastewater nutrient removal in wastewater treatment plants (WWPTs) and receiving rivers.

 

<SNIP>

 

Conclusions: The current pandemic influenza medical response might result in the discharge of insufficiently treated wastewater into receiving rivers, thereby increasing the risk of eutrophication and contamination of drinking water abstraction points. Widespread drugs in the environment could hasten the generation of drug resistance. These results highlight the need for empirical data on the effects of antibiotics and antiviral medications on WWTP and freshwater ecotoxicity.

Supplemental Material

(1.8 MB) PDF.

 

The 48-page supplemental file provides a pretty good look at the assumptions used in this computational study.

 

A press release summarizes this study’s findings, portions of which follow:

 

Centre for Ecology & Hydrology

Public release date: 2-Mar-2011

Effectiveness of wastewater treatment may be damaged during a severe flu pandemic

Existing plans for antiviral and antibiotic use during a severe influenza pandemic could reduce wastewater treatment efficiency prior to discharge into receiving rivers, resulting in water quality deterioration at drinking water abstraction points.

 

These conclusions are published this week (2 March 2011) in a new paper in the journal Environmental Health Perspectives, which reports on a study designed to assess the ecotoxicologic risks of a pandemic influenza medical response.

 

<SNIP>

 

The research team concluded that, consistent with expectations, a mild pandemic (as in 2009) was projected to exhibit a negligible ecotoxicologic hazard. However in a moderate and severe pandemic nearly all WWTPs (80-100%) were projected to exceed the threshold for microbial growth inhibition, potentially reducing the capacity of the plant to treat wastewater.

In addition, a proportion (5-40%) of the River Thames was similarly projected to exceed key thresholds for environmental toxicity, resulting in potential contamination and eutrophication at drinking water abstraction points.

(Continue . . . )

 

As Professor Emeritus of Statistics at the University of Wisconsin George E. P. Box famously observed:

 

All models are wrong, but some models are useful.”

 

Until we actually see a severe pandemic combated by modern pharmaceuticals, it is impossible to know just how big the environmental impact will be. 

 

Computational models, such as the one above however, give us clues as to what might happen under various very specific scenarios.   

 

And what this study, and others in the past, have shown us is that the impact could be multi-faceted and pose significant public health ramifications.

 

The solution, of course, isn’t to withhold life saving antibiotics or antivirals during a pandemic. It is to recognize potential problems before they occur, and to devise contingency plans now on how to deal with them.

 

Much like the more famous Murphy’s law, the Law of Unintended Consequences is not a scientifically recognized law, as is Boyle’s or Torricelli’s.

 

Nevertheless, they can almost always be counted on introduce new complications anytime you attempt to to `fix something’.

 

Whether it is the creation of newly resistant organisms or the discharge of dangerous partially treated effluent into the environment, studies such as these give us new insight into unexpected problems we might face during a severe pandemic.

2 comments:

Andrew Singer said...

Good summary of a complex problem! Thanks.

Michael Coston said...

Thank you, Dr. Singer.

Very kind of you to leave a comment.

I'm glad you liked it.