Pa ge 1 Pa ge 11 American Journal of Life Science and Innovation (AJLSI) Heavy Metal Analysis in Crassostrea iredaleiCrassostrea iredalei (Slipper Oyster) from Dumangas and Barotac Nuevo, Iloilo, Philippines Carisma G. M. S.1, Campania N. F.1, Casipe B. J.1, Chua A. D. T.1, Consolacion J. R. I.1, Daylo D. K. S.1, Dela Cruz A. P. J.1, Escultero H. J. R.1, Fajardo O. M. G.1, Falsis H. I. D.1, Felecio J. R. B.1, Blancaflor J. M.1, Palmos R. J. P.1, Visitacion R.1, Leong-on M. S.1* Volume 4 Issue 2, Year 2025 ISSN: 2833-1397 (Online) DOI: https://doi.org/10.54536/ajlsi.v4i2.5047 https://journals.e-palli.com/home/index.php/ajlsi Article Information ABSTRACT Received: April 20, 2025 Accepted: May 22, 2025 Published: October 11, 2025 It is relevant to analyze the concentrations of heavy metals in C. iredalei. This study was conducted to analyze the concentrations of the heavy metal contents, such as copper (Cu), lead (Pb), and zinc (Zn) in C. iredalei from Dumangas and Barotac Nuevo, Iloilo, Philippines. The samples of C. iredalei were analyzed using flame atomic spectrophotometry, and results were compared to regulatory limits set by the International Shellfish Safety and Sanitation Standards. In the town of Dumangas, Pb (mean = 0.01mg/L; sd = 0.11;) Cu (10.44 mg/L; sd = 2.95); and Zn (mean = 3.35 mg/L; sd = 0.13) were within the accepted values set by the regulatory limits of the International Shellfish Safety and Sanitation Standard. The samples of C. iredalei were taken from March 31st and April 7th, 2023. On the other hand, in the town of Barotac Nuevo, Pb (mean = -0.09, mg/L s = 0.02); Cu (mean = 10.14 mg/L, sd = 0.95; and Zn (mean = 3.21 mg/L; sd = 0.10) were within were within the accepted values set by the regulatory limits of the International Shellfish Safety and Sanitation Standard, too. This implies that the C. iredalei samples from farms in towns Dumangas and Barotac, Iloilo, Philippines, were safe for consumption and do not pose threats concerning heavy metal intoxication. Keywords Crassostrea Iredalei, Heavy Metal Determination, Slipper Oyster, Spectrophotometry 1 College of Pharmacy and Medical Technology, University of San Agustin, Iloilo City, Philippines * Corresponding author’s e-mail: mleongon@usa.edu.ph INTRODUCTION A popular delicacy that is widely cultivated in the Philippines for human consumption is the slipper oyster, or Crassostrea iredalei (Monaya et al., 2022). Therefore, encouraging a sustainable economy will raise the fishing industry’s and its related sectors’ economic value (Rustia et al., 2023). It is a popular item throughout Asia due to its inexpensive cost, especially among the poor (Pakingking et al., 2022). One essential food source that may be found all across the coastal region is C. iredalei. The nation produced 40,736.89 metric tons (MT) of C in 2021. Western Visayas contributed 10,886.16 MT, the second- highest amount among the other regions (Department of Agriculture’s Bureau of Fisheries and Aquatic Resources, 2022). Meat production for domestic use is the primary objective of oyster farming. By 2020, it is anticipated that oyster production alone will be worth Php 1.552 billion. Nutrition, food security, and the battle against poverty depend on them because they are the primary source of food and money for poor fishermen (Lebata-Romos et al., 2023). Situated in the center of the Philippines, the Western Visayas region is one of the main suppliers of oysters. More farms are being established in the Western Visayas region as a result of the need for extra sources of income brought on by small-scale fishermen’s diminishing catch. However, contamination in aquatic biological systems has become much more common in recent years due to mining and agricultural activities (Noman et al., 2022). Heavy metals in coastal and estuarine ecosystems, along with other environmental pollutants, have raised concerns in environmental conservation (Wang et al., 2022). Oysters are filter feeders that can collect pathogens from surrounding waters, potentially causing foodborne diseases in consumers (Pakingking et al., 2022). Persistently polluted organisms absorb heavy metals, which can cause severe illnesses such food poisoning, liver damage, cardiovascular abnormalities, and even death (Anandkumar et al., 2018). Food contamination by toxic heavy metals is a worldwide environmental risk that impacts hundreds of millions of people. Their toxicity results in a broad range of harmful biological effects (Balali-Mood et al., 2021). Oysters are valued as delicacy, but their fitness for human consumption should be monitored, especially as they are believed to be hyper- accumulators of a number of dangerous metals, such as cadmium, copper, and zinc (Wang & Weng, 2018). Cellular processes such as growth, proliferation, differentiation, damage repair, and apoptosis are all hampered by heavy metals. Through the production of Reactive Oxygen Species (ROS), oxidative stress, enzyme inactivation, and weakened antioxidant defense, these metals cause toxicity. High levels of exposure to heavy metals, especially lead and mercury, can cause serious side effects such as kidney failure, bloody diarrhea, and colic in the abdomen (Tsai et al., 2017). Due to equipment problems, the Bureau of Fisheries and Aquatic Resources (BFAR) has not performed heavy metal analyses in the past four years, saving them for cases of oyster exportation outside of the country (R. Chua, personal communication, January 10, 2024). Therefore, it Pa ge 12 https://journals.e-palli.com/home/index.php/ajlsi Am. J. Life Sci. Innov. 4(2) 11-14, 2025 seems sense to investigate the levels of heavy metals in C. iredalei in Dumangas and Barotac Nuevo, Iloilo. The purpose of this study was to examine the levels of heavy metals in C. iredalei from Barotac Nuevo and Dumangas, Iloilo. In particular, this study was able to characterize the many types of heavy metals that are present in C, including lead (Pb), copper (Cu), and zinc (Zn). C iredalei, from the oyster farms at Barotac Nuevo and Dumangas, Iloilo, during the last week of March and first week of April 2024. Additionally, the study measured the amounts of Cu, Pb, and Zn in C. iredalei at the time of collection and determined the heavy metal concentration in C. iredalei with regard to the International Safety and Sanitation Standard for Shellfish. According to the study’s findings, it was safe to eat C. iredalei from the municipalities of Dumangas and Barotac Nuevo. In the last week of March and the first week of April 2024. The Pb, Cu, and Zn levels were within the permissible range established by the International Shellfish Safety and Sanitation Standards. MATERIALS AND METHODS Research Design The occurrence of heavy metals like lead (Pb), copper (Cu), and zinc (Zn) in oysters from Dumangas and Barotac Nuevo, Iloilo, was investigated using a descriptive quantitative design. Additionally, it determined that the concentrations of certain heavy metals were within permissible bounds. Research Setting Oyster farms in Dumangas and Barotac Nuevo provided the data for this investigation. The laboratory of a private institution in Iloilo City was used to examine the heavy metals. Ethical Considerations This study was approved by the ethics committee of a private university in Iloilo City. Data Collection Procedures Collection of C. iredalei: For two weeks, C. iredalei samples were taken every week from two locations: Dumangas and Barotac Nuevo. Preparation of Samples: In accordance with the techniques of Azevedo et al. (2019), Pakingking et al. (2022), and Villafuerte et al. (2022), the C. iredalei were taken out of their shells using a knife. During transportation, the meat and intravenous fluid were gathered in a zippered storage bag and kept on ice. A mortar and pestle were then used to defrost and homogenize the samples. After being moved to their individual crucibles, the homogenates were weighed at 25 grams apiece. After being dried at 105 °C in a Memmert Drying Oven, the oyster samples were moved to a muffle furnace and heated for at least 24 hours at an increasing temperature of 450 °C to 500 °C. A desiccator was then used to chill the samples. Two milliliters of nitric acid were added to each oyster sample, which was then heated on a hot plate until it dried. To get carbon-free ash, this process was carried out at least twice. The samples were cooked on a hot plate with ten milliliters of 1N hydrochloric acid until all of the ashes had been dissolved. Following a 2.5 millimeter pore size Whatman Grade 5 filter, the materials were moved to a 25 milliliter volumetric flask. Detection of Heavy Metals: A flame atomic absorption spectrophotometer (Agilent AA55 MY1546001) was used to measure the levels of Cu, Pb, and Zn in the filtered digests. The stock standard solution was diluted to a concentration of 1000 micrograms per milliliter (µg/mL) or parts per million (ppm) in order to create all of the heavy metal standard solutions. The stock solution was then further diluted into concentrations of 0.300, 0.500, 0.700, 1.000, and 1.500 µg/mL to create the working standard solutions. Every result was expressed in parts per million or milligrams per liter. Analytical grade substances were used in this investigation. A certified chemist examined and verified the study. Five (5) replicates of each of the two (2) sets of samples were examined. Interpretation of Results: The mean and standard deviation were used to determine whether the results fell within the range of the International Shellfish Safety and Sanitation Standards, which are regulatory limits established by the Food and Drug Administration and the European Union. RESULTS AND DISCUSSIONS The results showed that the Zn (mean = 3.35 mg/L; sd = 0.13), Cu (mean=10.44 mg/L; sd = 2.95), and Pb (mean = 0.01 mg/L; sd = 0.11;) in the municipality of Dumangas were all within the acceptable levels established by the International Shellfish Safety and Sanitation Standard (Table 1). The C. iredalei samples were taken from March 31 and April 7, 2023. On the other hand, Pb (mean = -0.09 mg/L, s=0.02), Cu (mean = 10.14 mg/L, sd = 0.95), and Zn (mean = 3.21 mg/L, sd = 0.10) were all within the permitted limits established by the International Shellfish Safety and Sanitation Standard in the town of Barotac Nuevo. Table 1: Concentrations of Heavy Metals in C. iredalei Collected from Dumangas, Iloilo, Philippines Heavy Metal Accepted Value Concentration (mg/L) Mean SD Interpretation Pb 1.5 0.01 0.12 Within accepted values Cu 100 10.44 3.23 Within accepted values Zn 150 3.35 0.14 Within accepted values Pa ge 13 https://journals.e-palli.com/home/index.php/ajlsi Am. J. Life Sci. Innov. 4(2) 11-14, 2025 Table 2: Concentrations of Heavy Metals in C. iredalei Collected from Barotac Nuevo, Iloilo, Philippines Heavy Metal Accepted Value Concentration (mg/L) Mean SD Interpretation Pb 1.5 -0.09 0.02 Within accepted values Cu 100 10.14 1.04 Within accepted values Zn 150 3.31 0.11 Within accepted values Discussion Zinc, copper, and lead in C. iredalei that were gathered from the municipalities of Dumangas and Barotac Nuevo, Iloilo met the The International Shellfish Safety and Sanitation Standard’s permissible limits. These heavy metals’ comparatively low levels in C. iredalei can be ascribed to the sampling locations’ seclusion from mining operations and industrial industries. The farms where the C. iredalei were gathered and isolated from other rivers in the area. According to Noman et al. (2022), contemporary mining and farming methods have the potential to contaminate aquatic biological systems, which in turn may affect the levels of heavy metals in aquatic invertebrates like C. iredalei. Zinc and copper were the most prevalent metals found because of Cu and Zn-based agricultural products that are widely used in nearby shrimp and fish-rearing ponds. The levels of these heavy metals were found to be consistent with the findings of Pakingking et al. (2022) in their examination of slipper oyster farming areas of the Cogon and Palina Rivers and Cabugao Bay (in Roxas City and the Municipality of Ivisan, respectively, Capiz Province, Western Visayas, Philippines). Concentrations of lead, cadmium, mercury, and chromium, meanwhile, were below the legal thresholds established by the US and the EU. The Food and Drug Administration. Additionally, research by Ochoa et al. (2013) found that the concentrations of heavy metals in oysters cultivated in Catalonia, Spain’s Ebro Delta were largely similar to those found in earlier studies conducted in various unpolluted areas. This suggests that the higher exchange rate with marine water in bays where oysters are grown results in a decrease in metal levels. Since zinc and copper are regarded as necessary nutrients for the typical growth and development of C. iredalei, the comparatively greater quantities of these elements are to be expected (Ochoa et al., 2013). According to Pan and Wang (2009), aquatic invertebrates contain copper, and the bioaccumulation of this element might rise in direct proportion to the size of the animal. Natural cofactors in enzymatic processes within cells are Zn and Cu, which occur as ions (Zn2+ and Cu2+), and high levels of these metals are obtained by C. iredalei through their diet. Because Pb has been frequently linked to human poisonings, periodic monitoring of harmful metals in oysters should continue even though the concentration was below permissible levels (Balali-Mood et al., 2021). According to this study, C. iredalei can be safely consumed because heavy metals like lead, copper, and zinc were within permissible bounds. However, ongoing observation is necessary. Only the quantity and interpretation of lead, copper, and zinc from C.iredalei samples collected between March 31 and April 7, 2024, from the municipalities of Dumangas and Barotac Viejo, Iloilo, are covered by the findings. CONCLUSION As of the last week of March and the first week of April 2024, the levels of lead, copper, and zinc in C. iredalei from Dumangas and Barotac Nuevo were within the permissible range established by the International Shellfish Safety and Sanitation Standard. In terms of heavy metal intoxication during those months, the C. iredalei samples were safe to eat. It is advised that heavy metals, such as Cu, Pb, and Zn, be continuously monitored in C. iredalei, not just in Dumangas and Barotac Nuevo, Iloilo, but across the region. Measuring the concentrations of chromium, iron, and cadmium might also help future studies build on the current findings. REFERENCES Anandkumar, A., Nagarajan, R., Prabakaran, K., Bing, C. H., & Rajendran, R. (2018). Human health risk assessment and bioaccumulation of trace metals in fish species collected from the Miri coast, Sarawak, Borneo. Marine Pollution Bulletin, 133, 655–663. https://doi.org/10.1016/j.marpolbul.2018.06.033 Azevedo, J. a. M., Barros, A. B., De Miranda, P. R. B., Da Costa, J. G., & Nascimento, V. X. (2019). Biomonitoring of Heavy Metals (Fe, Zn, Cu, Mn, Cd, and Cr) in Oysters: Crassostrea rhizophorae of Mangrove Areas of Alagoas (Brazil). Brazilian Archives of Biology and Technology, 62. https://doi. org/10.1590/1678-4324-2019180211 Balali‐Mood, M., Naseri, K., Tahergorabi, Z., Khazdair, M. R., & Sadeghi, M. (2021). Toxic mechanisms of five heavy metals: mercury, lead, chromium, cadmium, and arsenic. Frontiers in Pharmacology, 12. https://doi. org/10.3389/fphar.2021.643972 Department of Agriculture’s Bureau of Fisheries and Aquatic Resources (DA-BFAR) (2022). Philippine Fisheries Profile 2021. https://www.bfar.da.gov. ph/wp-content/uploads/2022/11/2021-Fisheries- Profile-FINAL-F ILE.pdf Lebata-Ramos M. J. H. L. (2023). Molluscan aquaculture in the Philippines: a review. Environmental science. Processes & impacts, 20(6), 892–912. https://link. springer.com/article/10.1007/s10499-023-01120- 9 Monaya, K. J., Gomez, H. L., Tejano, L., & Peralta, J. M. (2022). Production and Characterization of Protein Isolates and Hydrolysates from Slipper Cupped Oyster (Crassostrea iredalei). The Philippine Journal of Pa ge 14 https://journals.e-palli.com/home/index.php/ajlsi Am. J. Life Sci. Innov. 4(2) 11-14, 2025 Science, 151(3). https://doi.org/10.56899/151.03.06 Noman, M. A., Feng, W., Zhu, G., Hossain, M. B., Chen, Y., Zhang, H., & Sun, J. (2022). Bioaccumulation and potential human health risks of metals in commercially important fishes and shellfishes from Hangzhou Bay, China. Scientific Reports, 12(1). https:// doi.org/10.1038/s41598-022-08471-y Ochoa, V., Barata, C., & Riva, M. C. (2013). Heavy metal content in oysters (Crassostrea gigas) cultured in the Ebro Delta in Catalonia, Spain. Environmental Monitoring and Assessment, 185(8), 6783–6792. https:// doi.org/10.1007/s10661-013-3064-z Pakingking, R. V., Hualde, M. L., Peralta, E. M., Faisan, J. P., & Usero, R. C. (2022). Microbiological Quality and Heavy Metal Concentrations in Slipper Oyster (Crassostrea iredalei) Cultured in Major Growing Areas in Capiz Province, Western Visayas. Pan, K., & Wang, W. (2009). Biodynamics to explain the difference of copper body concentrations in five marine bivalve species. Environmental Science & Technology, 43(6), 2137– 2143. https://doi. org/10.1021/es802888u Philippines: Compliance with International Shellfish Safety and Sanitation Standards. Journal of Food Protection, 85(1), 13–21. https://doi.org/10.4315/jfp- 21-257 Rustia, J. M., Antonino, J. P., Velasco, R. R., Lima, M. A., Yates, E. A., & Fernig, D. G. (2023). History and Prospects for the Sustainability and Circularity of the Windowpane Oyster Placuna Placenta Fishery in the Philippines. Fishes, 8(10),493. https://doi. org/10.3390/fishes8100493 Tsai, M.-T., Huang, S.-Y., & Cheng, S.-Y. (2017). Lead poisoning can be easily misdiagnosed as acute porphyria and nonspecific abdominal pain. Case reports in emergency medicine 2017. Case Rep. Emerg Med. 2017 (2), 1–4. https://doi.org/10.1155/2017/9050713 Villafuerte, C. G., S., Laburada, F. L., Q., Hofeleña, J. M., P., Rioja, A. L., D., & Villoso, K. N., V. (2022). Bioaccumulation and health risk assessment of heavy metals in slipper-shaped oysters (magallana bilineata) from barotac nuevo and dumangas, iloilo [Bachelor’s Thesis]. University of San Agustin.