Risk Assessment of Phthalate in Sur-face Water and Tap Water of U-Tapao Canal songkhla Province Southern Thailand

Abstract

PAEs are synthetic chemical compounds that causes endocrine disrupting effects in aquatic organisms such as algae, crustaceans fish and aquatic mammals, terrestrial biota as well as human. In human, prolonged exposure to PAEs may cause adverse health effects such as birth defects, alteration of semen quality, disruption of the hormonal and endocrine systems which may result to premature breast development, reduced gestation period, infertility in both male and female organism, testicular dysgenesis, childhood social impairment, obesity, asthmatic attack and breast cancer in human. Because of their ubiquitous presnces and potentila risk in aquatic ecosystems and human, a cross sectional study on the contamination of PAEs in water and sediment was carried out in U-Tapao canal, Songkla Province, southern Thailand. In addition, the efficiency of removing PAEs by water filtration plants, the sedimentary transfer of PAES, ecological and human health risks of PAEs were also assessed. Samples of surface water, tap water and sediment were collected and analyzed by GC- MS for six PAEs including di-n-butyl phthalate (DnBP), butyl-benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP)), di-iso-nonyl phthalate (DiNP), di-iso-decyl phthalate (DIDP). Seventeen sampling sites were chosen for surface water and sediments. Tap water samples were collected from four waterworks that received raw water from U-Tapao canal. All samples were collected during August 2018 to February 2019. The individual levels of PAEs detected in surface water ranged from 1.28±0.15 to 5.28±0.89 μg/L, non-detectable (ND) to 3.36±0.22 μg/L and ND 3.44±0.27μg/L for DEHP, DnBP and DiNP, respectively. The removal efficiency of PAES by the conventional water filtration plants ranged from 43%, 16.4% and 14.3% for DnBP, DiNP and DEHP, respectively. The estmated inventory indicated sedimentary PAES transfer of 12.2 tons into Songkhla lake in a period of 5 years, suggesting annual transfer of 2.44 tons and a potential source of PAES pollution of the largest natural lagoon in Thailand. The distribution of PAES along the network of the canal revealed that the sampling sites in the urban region were more contaminated with PAEs than those in rural region, thus associating the major source of PAES pollution of the investigated canal to urbanization. The ecological risk assessment indicated that PAEs posed moderate to high risks on sensitives organisms such as algae, crustaceans and fish in U-Tapao canal ecosystem. Human health risk assessment revealed that, the hazard quotient (HQ) for DnBP, DEHP and DiNP were below1, indicating acceptable risk of PAEs via ingestion or bathing of tap water. In addition, the Hazard Index (HI) via ingestion and bathing of tap water were less than1 indicating acceptable risks. Which implies that none of these PAEs congeners will cause any bad health effects on children, adolescents and adults through ingestions and bathing of tap water. Similarly, the cancer risk evaluated for DEHP, the only PAES congener classified as carcinogenic agent showed acceptable risk compared to 1.0 × 10 6 as stipulated by WHO. This suggest that the level of DEHP in the investigated tap water cannot trigger cancer risk in children, adolescents and adults via ingestion and bathing. However, considering the fact that PAES are endocrine disrupting organic pollutants, there is need to include PAEs in routine chemical monitoring programs and initiatives to limit both point and non-point source of PAES pollution of the canal. This will greatly enhance the prevention and protection of this freshwater, which is a major water resource for drinking water, balancing aquatic ecosystem, industrial and agricultural utilizations from further PAEs contamination. In addition, to mitigate ecological and human health risks of the sensitive aquatic habitats and Thai residents who use water and consume aquatic foods from the canal, respectively.