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Mexico City
Haoyu Zhao (MLA I ‘20)
The project investigates the chemosphere in the soil of Mezquita valley and its connection to Mexico City. Each day, a large number of pharmaceuticals and their metabolites are released to the city’s sewer system and drained to the Mezquita valley, where the untreated water directly irrigates the agricultural soil. The research understood the material flows of pharmaceutical production, consumption, and the environmental fate of several significant pharmaceuticals. By representing the soil in the language of pharmaceuticals breakdown products, we unraveled the dynamic landscape of health, economy, and political struggle in Mexico City and its consequence in the agriculture in Mezquital valley.
In Lesser’s investigation on 218 organic contaminants found in Mezquital Valley, Metformine, Caffeine, Cocaine, and its metabolites, and DEET has been found most prominent in the soil. The four pharmaceutical reveal a direct connection to the consumption of pharmaceuticals in Mexico City.
Metformin is a pharmaceutical targeted for type 2 diabetes, the recent growing population suffering from type 2 diabetes in Mexico City explained the wide distribution of these chemicals in the soil of Mezquital Valley. However, Galega officinalis, the base for metformin extraction, is a typical temperate plant thrives in Europe and Asia. The consumption and normalization of Metformin stimulate the oversea imports of Metformin and create a landscape of globalization that the chemical residues in the agricultural soil are alien to its native chemosphere. Metformin enters the aquatic environment through human waste, suggesting domestic bathroom, and toilet and the blackwater is the major venue where the chemicals exposed to the environment. Recent studies have also suggested that Metformin, although resistant to the human metabolic system, once released to the water, can be transformed into Guanylurea in the chlorination process of water treatment plants. Guanylurea is a chemical that is more resistant to biodegradation, and few studies have been able to understand its environmental impact.
Cocaine and its metabolite, Benzoylecgonine, also reveals the drug abuse problem in Mexico City. The use of cocaine and other drugs has been partly attributed to the drug trafficking activities in Mexico. Cocaine consumption first rises in the 90s and stay growing afterward, and the population related to cocaine use varied in ages and income levels. Even only makes up a little portion of the total organic contaminant detected in the water of Mezquital Valley, cocaine and its environmental fate is better understood than other pharmaceuticals due to its criminal nature. Similar to Metformin, Cocaine and Benzoylecgonine enters the environment through human waste.
For DEET and Caffeine, both of the drugs are subjects to daily usage. Caffeine enters the environment through urine. DEET, as a widely used insect and acarid repellent, it enters the aquatic surface through everyday human activities such as showering or bathing, and laundering of clothes has been applied with DEET.
Lesser, Luis E, Abrahan Mora, Cristina Moreau, Jürgen Mahlknecht, Arturo Hernández-Antonio, Aldo I Ramírez, and Héctor Barrios-Piña. "Survey of 218 Organic Contaminants in Groundwater Derived from the World's Largest Untreated Wastewater Irrigation System: Mezquital Valley, Mexico." Chemosphere 198 (2018): 510-21.
“Galega Officinalis.” Wikipedia. Wikimedia Foundation, April 14, 2020. https://en.wikipedia.org/wiki/Galega_officinalis.
Scheurer, Marco, Amandine Michel, Heinz-Jürgen Brauch, Wolfgang Ruck, and Frank Sacher. "Occurrence and Fate of the Antidiabetic Drug Metformin and Its Metabolite Guanylurea in the Environment and during Drinking Water Treatment." Water Research 46, no. 15 (2012): 4790-802.
Brouwer, Kimberly C, Patricia Case, Rebeca Ramos, Carlos Magis-Rodríguez, Jesus Bucardo, Thomas L Patterson, and Steffanie A Strathdee. "Trends in Production, Trafficking, and Consumption of Methamphetamine and Cocaine in Mexico." Substance Use & Misuse 41, no. 5 (2006): 707-27.
Zooplankton, Needle, Toilet, Tire, Stethoscope, Lilac
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Mezquital
Lu Dai (MLA I AP ‘20)
The project investigates the chemosphere in the soil of Mezquita valley and its connection to Mexico City. Each day, a large number of pharmaceuticals and their metabolites are released to the city’s sewer system and drained to the Mezquita valley, where the untreated water directly irrigates the agricultural soil. The research understood the material flows of pharmaceutical production, consumption, and the environmental fate of several significant pharmaceuticals. By representing the soil in the language of pharmaceuticals breakdown products, we unraveled the dynamic landscape of health, economy, and political struggle in Mexico City and its consequence in the agriculture in Mezquital valley.
Through the sewage pipe, a large number of pharmaceuticals flow from mexico city to mezquital valley, but only 70 types of pharmaceuticals are detected in the wastewater and 23 types in underground water, which means some pharmaceuticals break down during the transportation process or degrade in the soil.
Among the pharmaceuticals we find in Mezquital Valley, metformin and caffeine are the two most frequently detected while in underground water, a large amount of benzoylecgonine (the metabolite of cocaine) and deet have been found. For metformin and caffeine, they have been highly degraded in soils by bacterias and scientists prove that the break down process are affected by the moisture and temperature in the soil. 1,7-dimethylxanthine(the metabolite of caffeine) and guanyluree(the metabolite of metformin) will stay stable in soil and slowly be mineralized to molecules. However, for benzoylecgonine or deet,since they are stable in soil so they can reach groundwater and pose threat for human drinking water. Furthermore, deet has been proved to be toxic for some fresh water fish like rainbow trout and tilapia, and it has shown negative impact for freshwater zooplankton. Benzoylecgonine on the other hand, are affecting the cultivation of beans and aloes in Mezquital Valley.
These well known metabolisms are only small part of story of pharmaceuticals in the wastewater or Mezquital Valley. We can only test for what we made in our laboratories but cannot identify the unknown chemicals and the breakdown process of all the components.Current research focuses more on the first phase of metabolism but not the second or further degradation. Moreover, the breakdown products which enter the underground water will spread through the water flow that we are unable to track its distribution. Still, how these pharmaceuticals will transform and affect the ecosystem or human health in Mezquital Valley remains mostly undiscovered.