Licit and illicit drugs
Until the mid-2000s, the emerging study of pharmaceuticals in the environment inexplicably excluded illicit drugs. Illicit drugs are a structurally diverse group of chemicals used in enormous quantities worldwide that are very likely to affect humans and other non-target organisms; and just like pharmaceuticals, can enter the environment via many pathways. It had been known for decades that illicit drugs and their breakdown products are excreted in urine, faeces, hair, and sweat; but this was ignored until 1999 when the United Nations included illicit drugs in its scope of concern.
However, the United Nations drug control conventions still do not recognize a distinction between licit and illicit drugs; they describe only use to be licit or illicit. The term ‘illicit drugs’ designates drugs that are under international control (and may or may not have licit medical purposes), but are produced, trafficked and/or consumed illicitly .
The first published indication that illicit drugs might be pervasive contaminants of our environment was a 1987 FBI study showing that cocaine was present on money in general circulation. Later surveys found illicit drugs in sewage wastewaters, surface waters, air, sewage sludge, and drinking water. The illicit drugs commonly encountered in the urban environment include codeine, morphine, methadone, amphetamine, methamphetamine, cocaine, tetrahydrocannabinol (THC) and the primary metabolites of methadone. Although widely detected in clinical and forensic drug screens, the occurrence of heroin (diacetylmorphine) in the environment is limited primarily to banknotes, because of its propensity to hydrolyse in water.
Illicit drugs in the environment
Illicit drugs and their metabolites in the environment and their potential impact on the ecosystem is a growing concern. Cocaine, morphine, amphetamine, and MDMA have potent pharmacological activities and their presence as complex mixtures in water may well have adverse effects on aquatic organisms and human health. However, there is no regulation over the presence of these pollutants in treated wastewater, surface water, drinking water, or the atmosphere.
The concentrations (in ng/L) of illicit drugs in wastewaters and surface waters from around the world are compiled in two categories: cocainics, opioids, and cannabinoids; and amphetamine and ecstasy group compounds. The range spans three to four orders of magnitude (see Table 1) .
Table 1 Illicit Drugs in Water
|Wastewater ng/L||Surface water ng/L|
|Cocainics, opioids, & cannabinoids||18.8 – 7 500||7.5 – 3 425||0.1 – 316|
|Amphetamine & ecstasy group||2.2 – 15 380||1.0 – 10 955||0.4 – 309|
Extensive reviews from around the world reveal widespread pollution of water by illicit drugs. The data provide information on drug abuse that cannot be obtained from conventional epidemiology. Even more importantly, they highlight the need for remediation in order to restore the quality of urban drinking water .
Illicit drug consumption and sewage epidemiology
Drug consumption by wastewater analysis was carried out in Paris. Cocaine and its metabolite, amphetamine, MDMA (ecstasy) and buprenomorphine were compared in the areas around four water treatment plants. Drug consumption differed in the four areas, being most prevalent during weekends. The estimated illicit drug-taking in Paris were lower than in other countries such as Spain and Italy . In Australia, wastewater analysis showed that in one year (from 2009 to 2010), the use of MDMA declined fifty fold with a rise in methamphetamine use . Similar sewage epidemiology in the state of Oregon, USA, showed that cocaine use was mainly in urban settings and low or absent in rural areas . MDMA was used in less than half of the communities, mainly in urban settings; while methamphetamine was used in all communities, whether urban and rural .
Three unnamed Canadian cities were studied for the use of cocaine, amphetamine, methamphetamine and MDMA. The highest methamphetamine use was in the largest of the cities, while ecstasy and cocaine use was lowest in the smallest city . The Canadian study violated a prime directive of science reporting by failing to identify the cities and wastewater plants studied; consequently, the experiments could never be repeated independently.
A study of surface waters from the Tagus River flowing through the province of Toledo (downstream of Madrid metropolitan area) and drinking waters in two nearby cities detected 12 out of 22 drugs of abuse at concentrations ranging from 1.14 to 40.9 ng/L . Even as these relatively low concentrations, effects on wildlife or human health cannot be disregarded, especially in vulnerable populations.
Cleansing drinking water polluted with illicit drugs
Drinking water polluted with illicit drugs has been deemed acceptable by government agencies including the World Health Organization, the European Union, the US Environment Protection Agency in clear violation of the precautionary principle with regard to public health and safety.
A photo-Fenton process has been shown to be remarkably effective in degrading the illicit drugs , and involves treating water with ferrous iron and hydrogen peroxide in the presence of ultraviolet light.
A recent review includes removal of illicit drug pollutants by conventional treatment technologies as well as advanced treatments such as membrane bioreactors . Membrane bioreactor (MBR) technology is considered the most promising development in microbiological wastewater treatment. Several studies clearly outlined its strong potential for reducing ecological risks associated with illicit drugs as well as other polar micro pollutants. Bank filtration is a type of filtration that purifies water by passing the water through the banks of a river or lake. It is then extracted by wells located some distance away from the water body. Bank filtration does not guarantee the complete removal of all potential illicit drug residues present in the water. It can be regarded as a useful tool for the pre-treatment of raw water (wastewater, surface water and reclaimed water), which then requires further purification to produce drinking water.
Aptamers are a new class of single-stranded DNA/RNA molecules selected from synthetic nucleic acid libraries for molecular recognition  (see Aptamers for Biosensing, Diagnosis, Drug Delivery and Therapy, SiS 56). A novel aptamer column for removing trace drug pollutants in drinking water was developed. Cocaine and diclofenac (an anti-inflammatory drug) were chosen as model molecules to test the aptamer column. The removal of the illicit drug was as high as 88-95% .
Moral and ethical issues in sewage epidemiology
A 2012 report from Australia deals with some legal ramifications in the use of site-specific wastewater analysis of illicit drug use in prisons and or sites such as nightclubs or music festivals . The article from a law journal concludes that producing anonymous, non-identifiable data is essential for a number of reasons, including that the studies concern illegal activities, namely drug possession and trafficking. It states that for prison studies, it is important that publications do not name the facilities at which the research was conducted. Aside from alleviating concerns over negative media exposure, it is deemed important to protect the anonymity of participating prisons to avoid stigmatizing inmates, their families and prison staff.
I disagree. The outlook of lawyers conflicts with the foundation of science that research results should be reported fully and truthfully. Publications in science journals should require that large anonymous samples such as those used in sewage epidemiology should report the time and place of sample collection and analysis. It is, further, a matter of public health, especially for those who are forced to suffer the consequences of water pollution, without their knowledge or consent.
The growing pollution of surface and drinking water with illicit drugs and their by-products is a matter of concern. Like pharmaceutical drug pollution, the levels observed are sufficient to affect aquatic organism but claimed to be of no major concern for humans according to regulatory authorities. Precaution demands that the public be alerted to the growing threat to drinking water. The locations where drinking water is polluted with illicit drugs should not be withheld from the population affected.