The bell rings during a hot day in Pinalagad Elementary School, a primary school in Pinalagad, Valenzuela City (a poor dumpsite community in Metro Manila), and children come running out of their classrooms. Without water fountains within the school grounds, some students drink directly from the faucets without being aware of the health risks that the water has. In a small and poor community such as Pinalagad, how can we test its waters for toxicity in a cheap, efficient, and reliable manner? Students from Valenzuela City conducted an Allium cepa chromosome aberration assay on the waters from public elementary schools in Valenzuela to determine the level of toxicity that is present in the tap water sources.
Allium cepa chromosome aberration assay
The Allium cepa chromosome aberration assay is a cheap, efficient, and reliable method for testing genotoxicity. The materials used in the assay are cheap and easy to find in any laboratory set-up; thus, it may be easily conducted by student scientists. This is conducted by treating an onion’s root tips with the liquid solution being tested and observing the number of aberrant cells that will be present in the elongated onion root tips after a couple of weeks. Once the root tips are prepared for microscope viewing (there are different methods on how to prepare the onion root tip microscopic cross-sections), the number aberrant cells growing in the meristematic region will determine the genotoxicity of the liquid solutions. There are different types of aberrations that can be found in the cell. Most of the time, researchers focus on the anaphase-telophase chromosomal aberrations as they are easier to observe and determine. Furthermore, Allium cepa chromosome aberration assay has been conducted on substances such as agricultural soils (1), steel fabrications (2), even Chernobyl-contaminated soils (3).
The water from Pinalagad Elementary School was collected and then used to treat the root tips of onions. The Allium cepa chromosome aberration assay was conducted and the aberrant cells from all phases of mitosis (prophase, metaphase, anaphase, and telophase) were quantified and observed through the comparison of mitotic indices. The mitotic indices were computed by totaling the number of aberrant cells over the total number of dividing cells. The results showed that the tap water from Pinalagad Elementary School was approximately 60% genotoxic (4). Factors such as the environment of the school or the pipes used by the water provider may have contaminated the water with genotoxic substances such as benzene, xylene, and toluene.
Aside from Pinalagad Elementary School, there are still several regions around the globe in which access to clean, cheap, and potable water are hard to come by. Even though households have access to clean tap water, there is still no assurance that the water being used in their daily household functions are free from genotoxic substances. Furthermore, how much more will the damage of genotoxic substances reach without mitigation from results of genotoxic assessments? Something as simple as an onion can be our window to pertinent concerns such as water quality in scarce regions in the world.
- Soodan, Rajneet Kour, Jatinder Kaur Katnoria, and Avinash Nagpal. “Allium cepa root chromosomal aberration assay: An efficient test system for evaluating genotoxicity of agricultural soil.” J. Sci. and Res(2014): 3-8.
- Barbhuiya, Sweety Nath, et al. “Two Major Components of Steel Fabrication Industry, Benzene and Thinner Induce Cytotoxicity in Allium cepa L. Root Cells.” Cytologia2 (2018): 155-158.
- Kovalchuk, Olga, et al. “The Allium cepa chromosome aberration test reliably measures genotoxicity of soils of inhabited areas in the Ukraine contaminated by the Chernobyl accident.” Mutation Research/Genetic Toxicology and Environmental Mutagenesis1 (1998): 47-57.
- Banares, Lhiana Reign S. Evaluation of Genotoxicity in Tap Water Samples From Public Elementary Schools in Valenzuela City Using Allium Cepa Chromosomal Aberration Assay. September, 2015.