Population Normalization with Ammonium in Wastewater-Based Epidemiology: Application to Illicit Drug Monitoring

Abstract

Fluctuations in ammonium (NH4+), measured as NH4-N loads using an ion-selective electrode installed at the inlet of a sewage treatment plant, showed a distinctive pattern which was associated to weekly (i.e., commuters) and seasonal (i.e., holidays) fluctuations of the population. Moreover, population size estimates based on NH4-N loads were lower compared to census data. Diurnal profiles of benzoylecgonine (BE) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) were shown to be strongly correlated to NH4-N. Characteristic patterns, which reflect the prolonged nocturnal activity of people during the weekend, could be observed for BE, cocaine, and a major metabolite of MDMA (i.e., 4-hydroxy-3-methoxymethamphetamine). Additional 24 h composite samples were collected between February and September 2013. Per-capita loads (i.e., grams per day per 1000 inhabitants) were computed using census data and NH4-N measurements. Normalization with NH4-N did not modify the overall pattern, suggesting that the magnitude of fluctuations in the size of the population is negligible compared to those of illicit drug loads. Results show that fluctuations in the size of the population over longer periods of time or during major events can be monitored using NH4-N loads: either using raw NH4-N loads or population size estimates based on NH4-N loads, if information about site-specific NH4-N population equivalents is available.

Wastewater-Based Epidemiology of Cocaine in the Brazilian Federal District: Spatial Distribution, Weekly Variation and Sample Preservation Strategies

“…Also for this reason, analytical data concerning benzoylecgonine in wastewater samples has been used as a near real-time tool to estimate cocaine consumption for a given population. 8,9 Several works have explored different aspects of the WBE approach including other cocaine metabolites, 10 estimation of other consumed drugs, 10-12 influence of recreational events, [13][14][15][16] consumption dynamics in restricted facilities, [17][18][19] temporal and spatial variability, [20][21][22] stability of target chemicals, 23,24 refinement on estimates calculation, [25][26][27] innovations in sample preparation and analysis, [28][29][30] among others. In Brazil, the first work to put the WBE approach into practice was designed to assess cocaine consumption on regions served by six wastewater treatment plants (WWTP) installed in the Brazilian Federal District (FD).…”

Refining the uncertainties and expansion of wastewater-based epidemiology for assessing population exposure to chemicals

“…(van Nuijs et al 2011c) Our data also follow the result of another recent study which revealed consistent patterns of per capita illicit drug use between using census data (de jure 220,000 persons) and estimated population numbers using ammonium ions in the urban area of Lausanne, Switzerland. (Been et al 2014) These coherent findings among international studies in large catchments indicate that the consumed mass of illicit drugs varies more substantially than the population, and consequently, relative temporal changes of population drug consumption usually persist irrespective of the type of population estimates used for normalization. This may not be the case for small catchments and days with special events.…”

“…Human-specific chemicals were proposed but not validated in five studies, namely, creatinine, (Chiaia et al 2008), (Brewer et al 2012) coprostanol,(Daughton 2012a) cholesterol, cotinine, and a neurotransmitter metabolite, 5-hydroxyindoleacetic acid, (Chen et al 2013) and commonly prescribed pharmaceuticals and artificial sweeteners. (Lai et al 2011) Only two studies were found in which the measurement was over an extended period: one covered 235 days in a 1 year period using hydrochemical parameters (nitrogen, phosphorus, biological oxygen demand, and chemical oxygen demand), and another one covered 13 days in an 8 month period using ammonium; (van Nuijs et al 2011c), (Been et al 2014) those selected chemicals are not human-exclusive. Only one recent publication provides an approach to quantify objectively the methodological uncertainty of the population estimates.…”

“…A number of proxies have previously been proposed to address the population uncertainty. These include nutrients such as N and P, biological oxygen demand (BOD) and chemical oxygen demand (COD) (Been et al 2014, van Nuijs et al 2011c), creatinine (Brewer et al 2012), caffeine and nicotine (Senta et al 2015), as well as selected pharmaceuticals and personal care products (PPCPs) and an artificial sweetener (Lai et al 2011). But none of the proposed population markers were calibrated against accurate population counts and thus were not validated yet.…”

“…Alternative approaches have been proposed to estimate the de facto population including the use of several biomarkers to estimate the population contributing to a wastewater treatment plant for a given period (Been et al 2014, Chen et al 2013, Daughton 2012a. But until now only a set of commonly consumed pharmaceuticals and personal care products (PPCPs) have been evaluated as useful to estimate the population in different catchments in Australia (Lai et al 2011.…”