Team:TAS Taipei/Description
What Are Agricultural Contaminants?
Agricultural contaminants, such as heavy metals and pesticides, are chemical substances remaining in crops that are harmful to human health (Agriculture Victoria, n.d.). Heavy metals, such as copper, mercury, nickel, iron, lead, and cadmium, are commonly found in industrial waste runoff that contaminates farmland (Yang et al., 2018; Zhang et al., 2013; Jaishankar et al., 2014; Temple & Bisessar, 1981). Pesticides, such as insecticides, herbicides, fungicides, are substances that kill, repel, or control pests to maximize crop yields (Pesticide Action Network, 2015). Available estimates reveal global pesticide use has increased 50-fold since 1950, and 4 million tonnes of agricultural pesticides are used each year worldwide (Figure 1; Miller, 2011; Food and Agriculture Organization, 2019). We are constantly exposed to pesticides through ingestion of contaminated food or water.
Figure 1. Average pesticide use per area of cropland (kg/ha) from 1990 to 2016
(Food and Agriculture Organization, 2018).
The Problem With Contaminants
The main heavy metals people are exposed to through contaminated food and drinking water are lead, chromium, and arsenic (Jaishankar et al., 2014; Jarup, 2003). In general, exposure to heavy metals has detrimental health effects, including physical and neurological degeneration, and cancer (Jaishankar et al., 2014). For example, acute exposure to lead may result in high blood pressure, renal dysfunction, brain damage, or death (Jaishankar et al., 2014). In 2016, lead exposure was responsible for approximately 540,000 deaths worldwide (Figure 2; World Health Organization, 2018).
Figure 2. Deaths per 100,000 people from lead exposure in 2016 (Institute
for Health Metrics and Evaluation, 2017)
Moreover, chronic exposure to pesticides can lead to cancer, Alzheimer's disease, Parkinson's disease, endocrine disorders, development disorders, infertility, and even death (World Health Organization, 2018). In 2017, exposure to pesticides caused 200,000-300,000 deaths worldwide (UN News, 2017). One such class of toxic pesticides are organophosphates, which are commonly used as an effective insecticide (Karami-Mohajeri et al., 2011). Organophosphates function by irreversibly inhibiting the enzyme acetylcholinesterase, preventing the breakdown of the neurotransmitter acetylcholine. This inhibition results in the accumulation of acetylcholine in synapses and excessive stimulation of neurons, which disrupts the nervous system and kills the pests. Unfortunately, the same mechanism also affects humans (Alves de Castro et al., 2017).
Why should we care?
The problem of agricultural contaminants is especially concerning in East Asia, which has the highest pesticide usage per land area (Figure 3; Food and Agriculture Organization, 2018). Similarly, heavy metal contamination levels are rising in farmlands in East Asia (Arunakumara et al., 2013). For example, in many regions in China and Japan, the average cadmium concentration in the soil exceeds the established limits (Arunakumara et al., 2013; Oda et al., 2006).
Figure 3. Average pesticide use per area of cropland (kg/ha) from 1990 to 2016 by continent (Figure from
Food and Agriculture Organization, 2018).
Agricultural contaminants affect our home, Taiwan, as well. 787 hectares (the size of 1470 football fields!) of rural soil are heavily contaminated with heavy metals such as cadmium, lead, and nickel (Food and Fertilizer Technology Center, 2000). In addition, over the last few years, 10-15% of randomly sampled agricultural products in Taiwan exceed pesticide residue limits, compared to the 1-2% in the United States in 2016 and the European Union in 2017 (Taiwan Food and Drug Administration, 2018; U.S. Food and Drug Administration, 2016; European Union, 2019). Just last month, “21.6 percent of the tested items in Taipei had pesticide residue exceeding” the MRLs, according to Taipei Times, which is much higher than the 10-15 % reported by the Taiwanese FDA (Taipei Times 2019). Thus, we feel an immediate need to address this issue.
Current Detection Methods
Given the prevalence of heavy metals and pesticides in Taiwan, we want to develop a simple and convenient method to detect agricultural contaminants on food products.
Current lab methods to detect heavy metals, such as spectrometry, are usually expensive, complicated, and time-consuming (Sikdar, 2018). Though there are home testing kits available, these kits vary in accuracy and most lack approval from official governmental bodies. For pesticide residue detection, farmers typically send samples to pesticide-detection companies, such as Société Générale de Surveillance (SGS), that will help test residue levels on the samples using gas or liquid chromatography (Société Générale de Surveillance, 2019). However, our interview shows most farmers are unaware of the exact details behind lab testing, and this process does not provide immediate results for farmers.
A product that uses synthetic biology can address the shortcomings of current detection methods. Standardized BioBrick parts and restriction sites allow us to efficiently clone our DNA constructs. We obtained all the genetic parts we needed from the iGEM distribution kits, and could easily build and test different combinations of metal-binding or pesticide-binding proteins with colored proteins.
Our Goal
Our goal is to use synthetic biology to attach colored proteins to binding proteins that target heavy metals and pesticides.
We were inspired by Dr. Aaron Kyle, a Senior Lecturer of Biomedical Engineering at Columbia University, who was our school’s Visiting Scholar this year. He introduced to us many of his students’ projects, including the winning design for the Columbia Design Challenge: Confronting the Ebola Crisis. To improve the decontamination of biohazard suits, Dr. Kyle’s students designed a bleach spray with a blue dye that would help visualize the sterilized areas (National Public Radio, 2014; Columbia Magazine, 2014). Because we were amazed by the simple and elegant design of this solution, we decided to use a similar method for the detection of agricultural contaminants.
We envision our detection product to be a liquid spray containing colored residue-binding proteins; when applied to food products, the proteins will bind to agricultural contaminants and produce patches of color that will remain on the contaminated regions (Figure 4).
Figure 4. Protein Binding to Residues
References
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