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On 2016 Sep 21, Daniel Himmelstein commented:

Thanks Dr. Seulbe Lee for you response. My apologies for the unit mistake. For the record, I had incorrectly used milliliters rather than liters in the denominator of stream concentrations.

I updated my notebook to fix the error. To avoid confusion, I changed the notebook link in my first comment to be version specific. I also performed another analysis which speculated on potential sewage contentrations of AMPH under the following assumptions:

• 1 in 4 people orally consume 30 mg of AMPH daily
• 40% of the consumed AMPH is excreted into the sewage
• Each person creates 80 gallons of sewage per day

Under these assumptions, fresh sewage was estimated to contain 9.91 ug/L of AMPH, which is ~10 times higher than the artificial streams. Granted there is likely additional dilution and degradation I'm not accounting for, but nonetheless this calculation shows it's possible that sewage streams from avid amphetamine communities could result in the doses reported by this study.

Our research group is continuing work on the ecological effects of multiple contaminants found in these streams.

Glad to hear. As someone who's swam in both Cresheim Creek and the Mississippi River just this summer, I can appreciate the need to study and reduce the contamination of America's waterways.

On 2016 Sep 17, Sylvia Seulbe Lee commented:

Daniel,

Thank you for your comments on the paper. We appreciate your skepticism and critical observations. Although the CNN story mentions that the source of amphetamine in Baltimore streams could be linked to the excrement of illicit drug users, we clarify that our study made no claims about the major source of the amphetamine in the streams we sampled. Illicit or recreational drug use is one potential source of amphetamine. We are unable to distinguish between recreational and prescription drug use in Baltimore, but prescription use of amphetamine (e.g., for the treatment of ADHD, illicit use by college students prior to exams) may be the primary cause for increased loading, especially given the increasing trend in number of diagnoses and prescription of medication for treatment of ADHD and similar conditions. Another source of amphetamine is improper disposal of prescription medication (flushing down the toilet).

We have to point out that your reading of the amphetamine concentrations is incorrect. We measured 0.630 ug/L amphetamine in Gwynns Falls, which is equivalent to 630 ng/L or 0.630 ng/mL. Additionally, we added 1 ng/mL (equivalent to 1 ug/L reported in the paper) amphetamine into the artificial streams, not 1000 ng/mL. Thus, the actual concentrations of amphetamine measured in the field and used in the experiment were 1000 times less than the concentrations you reported.

With respect to dilution of pharmaceutical products from sewage to the watershed, we would like to note that the stream we sampled is small (http://www.beslter.org/virtual_tour/Watershed.html) and the wastewater entering these streams is mostly raw, untreated sewage leaking from failing infrastructure. Baltimore has a population of more than 600,000 people and the large number of people feeding waste into that river could create quite a load. In addition, we note that amphetamine degraded by over 80% in the artificial streams. Thus, we noted in the discussion section that the high concentrations found in the field may indicate that the loading of amphetamine into the Baltimore streams is actually higher than the concentrations we measured, or that there is pseudo-persistence of amphetamine because of continuous input into the streams. Our finding that there were ecological effects even with 80% degradation of the parent amphetamine compound in the artificial streams is noteworthy.

Furthermore, we acknowledge that the concentrations of drugs in streams is spatially and temporally variable. As shown in our paper, the concentrations of drugs differed quite a bit between our sampling in 2013 and in 2014. The differences were likely due to high flow events prior to our sampling date in 2013. However, the environmental relevance of 1 ug/L amphetamine concentration was clearly supported in the paper by higher concentrations found in streams and rivers in other locations (e.g., Spain, India, etc.).

Finally, we agree completely that there are many pressing and detrimental contaminants in urban streams in Baltimore and elsewhere. Our research group is continuing work on the ecological effects of multiple contaminants found in these streams.

Regards, Sylvia - on behalf of my co-authors.

On 2016 Aug 26, Daniel Himmelstein commented:

Preamble: I'm far from an expert on environmental science, just a critical observer skeptical of claims that excrement from recreational drug users harms aquatic environments. Given the ongoing war on drugs, these topics are bound to political. For example, CNN covered this study with the title "Your drain on drugs: Amphetamines seep into Baltimore's streams." The CNN story concludes that excrement of illicit meth users is of environmental concern.

Premise: By the time pharmaceutical products in excrement reach the watershed, they will be extremely diluted. Humans safely tolerate the undiluted dosage, so in general I don't envision the extremely diluted dose harming aquatic life. In cases where the watershed contains high concentrations of pharmaceuticals, I suspect the contamination vector was not the excrement of users, but rather runoff from manufacturing or distribution processes.

Specifics:

This study observed the following six concentrations of amphetamine in Baltimore's streams: 3, 8, 13, 28, 101, 630 ng/ml (Table 1). They constructed four artificial streams where they introduced 1000 ng/ml of AMPH (D-amphetamine). Note that the controlled experiment evaluated an AMPH concentration 49 times that of the median concentration in Baltimore streams.

Furthermore, the Cmax (max concentration in plasma) of D-amphetamine resulting from prescription Adderall is 33.8 ng/ml (McGough JJ, 2003). Accordingly, the artificial streams used an AMPH concentration 30 times that of the blood of an active user. Note that AMPH has a high bioavailability: 75% of the consumed dose enters the blood according to DrugBank. It's unreasonable that runoff from excrement of users could result in a higher concentration than in the blood of the active user.

However, the study frames the contamination as a result of excrement. The introduction states:

Unfortunately, many of the same chemicals are also used illicitly as narcotics. After ingestion of AMPH approximately 30−40% of the parent compound plus its metabolites are excreted in human urine and feces, and these can be transported into surface waters directly or through wastewater treatment facilities. On the basis of increases in both medical and illicit usage, there is cause to speculate that the release of stimulants to various aquatic environments across the globe may be on the rise.

And the discussion states:

Our study demonstrates that illicit drugs may have the potential to alter stream structure and function.

Conclusion:

Evidence is lacking that excrement from recreational drug users has anything to do with environmentally harmful levels of AMPH in Baltimore streams. There seems to be a bigger issue with pollution in the Baltimore streams, with the study stating:

As much as 65% of the average flow in the Gwynns Falls can be attributed to untreated sewage from leaking infrastructure

In such a polluted aquatic environment, I suspect there are several more pressing and detrimental contaminants than recreational drugs. Finally, there are related studies, such as Jiang JJ, 2015, that I haven't had time to investigate.

Update 2016-09-01:

Here is more evidence that the 630 ng/ml of amphetamine observed in Gwynns Run at Carroll Park is extremely high. At that concentration, only 7.94 liters of stream water contain an effective dose of AMPH (5 mg). At 1000 ng/ml, 5.0 liters of water contain an effective dose of AMPH.

On 2016 Aug 26, Daniel Himmelstein commented:

Preamble: I'm far from an expert on environmental science, just a critical observer skeptical of claims that excrement from recreational drug users harms aquatic environments. Given the ongoing war on drugs, these topics are bound to political. For example, CNN covered this study with the title "Your drain on drugs: Amphetamines seep into Baltimore's streams." The CNN story concludes that excrement of illicit meth users is of environmental concern.

Premise: By the time pharmaceutical products in excrement reach the watershed, they will be extremely diluted. Humans safely tolerate the undiluted dosage, so in general I don't envision the extremely diluted dose harming aquatic life. In cases where the watershed contains high concentrations of pharmaceuticals, I suspect the contamination vector was not the excrement of users, but rather runoff from manufacturing or distribution processes.

Specifics:

This study observed the following six concentrations of amphetamine in Baltimore's streams: 3, 8, 13, 28, 101, 630 ng/ml (Table 1). They constructed four artificial streams where they introduced 1000 ng/ml of AMPH (D-amphetamine). Note that the controlled experiment evaluated an AMPH concentration 49 times that of the median concentration in Baltimore streams.

Furthermore, the Cmax (max concentration in plasma) of D-amphetamine resulting from prescription Adderall is 33.8 ng/ml (McGough JJ, 2003). Accordingly, the artificial streams used an AMPH concentration 30 times that of the blood of an active user. Note that AMPH has a high bioavailability: 75% of the consumed dose enters the blood according to DrugBank. It's unreasonable that runoff from excrement of users could result in a higher concentration than in the blood of the active user.

However, the study frames the contamination as a result of excrement. The introduction states:

Unfortunately, many of the same chemicals are also used illicitly as narcotics. After ingestion of AMPH approximately 30−40% of the parent compound plus its metabolites are excreted in human urine and feces, and these can be transported into surface waters directly or through wastewater treatment facilities. On the basis of increases in both medical and illicit usage, there is cause to speculate that the release of stimulants to various aquatic environments across the globe may be on the rise.

And the discussion states:

Our study demonstrates that illicit drugs may have the potential to alter stream structure and function.

Conclusion:

Evidence is lacking that excrement from recreational drug users has anything to do with environmentally harmful levels of AMPH in Baltimore streams. There seems to be a bigger issue with pollution in the Baltimore streams, with the study stating:

As much as 65% of the average flow in the Gwynns Falls can be attributed to untreated sewage from leaking infrastructure

In such a polluted aquatic environment, I suspect there are several more pressing and detrimental contaminants than recreational drugs. Finally, there are related studies, such as Jiang JJ, 2015, that I haven't had time to investigate.

Update 2016-09-01:

Here is more evidence that the 630 ng/ml of amphetamine observed in Gwynns Run at Carroll Park is extremely high. At that concentration, only 7.94 liters of stream water contain an effective dose of AMPH (5 mg). At 1000 ng/ml, 5.0 liters of water contain an effective dose of AMPH.