Charita Kwan

University of the Philippines | UPD · Natural Sciences Research Institute

The study investigated the levels of heavy metals (Hg, As, Cd, Cr, Pb) in frequently consumed vegetables in urban and rural farms in the Philippines and assessed their associated health risks. Results revealed that the Hg concentration was at method detection limit (MDL), while for other heavy metals, the values ranged from <MDL to 0.09 mg/kg (As),...

Plastics are formed from C–C single bonds which are flexible making them easily transformable. Thus, plastics have been widely utilized by the global society. However, the C–C single bond is easily breakable by UV radiation. Eventually, plastics are fragmented into microplastics (<5 mm) and ultimately will be washed off to marine environments. Micr...

Polychlorinated biphenyls (PCBs) are a group of synthetic organic chemicals that enrich the food chain via biomagnification where the highest levels have been detected in cetaceans. While several studies have reported cetaceans as sentinels of environmental pollution, information on the contamination status of PCBs in cetaceans found stranded along...

Polybrominated diphenyl ethers (PBDEs) were measured in plastic resin pellets collected from 65 beaches across 27 countries worldwide. They were detected at 49 locations at concentrations of the sum of 49 congeners of up to 46 ng/g-pellet and a median of 2 ng/g-pellet. These values are one to two orders of magnitude lower than those of polychlorina...

Polycyclic aromatic hydrocarbons (PAHs) are one of the priority pollutants measured in atmospheric particles due to their potential health risks to exposed individuals. A miniaturized solvent extraction and cleanup method has been developed for the determination of 14 types of PAHs in air particulate matter (APM) collected through the use of a five...

Additives and monomers are integral components of plastics or polymers. Bisphenol A (BPA), nonylphenol (NP), and polybrominated diphenyl ethers (PBDEs) are the common monomer and additives used primarily to improve the quality of plastic materials. They are used as antioxidants, stabilizers, plasticizers, and flame retardants in plastics that are i...

1. Introduction The Philippines, composed of 7,000 islands, is one of the world’s largest archipelagos. With 78,000 km2 arable farmland and 17,500 km of coastline, a large part of an estimated 90 million population of the Philippines depends on agriculture and fisheries. As most other countries, the Philippines imported and used chlorinated pesti...

Historical trends of the accumulation of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in a typical tropical Asian environment were investigated using radio-dated sediment cores from Manila Bay, the Philippines and from the upper Gulf of Thailand. Vertical profiles indicated earlier usage of PCBs than of PBDEs which co...

Polybrominated diphenyl ethers (PBDEs) were measured in surface sediment samples collected from urban canals or rivers in Lao PDR, Cambodia, Vietnam, India, Indonesia, Thailand, the Philippines, Malaysia and Japan. The total PBDE concentrations in the sediments ranged from 0.83 to 3140ng/g dry wt. BDE-209 was predominant, ranging from 43% to 97% of...

Polybrominated diphenyl ethers (PBDEs) are extensively used as flame retardants in many consumer products, and leachates from landfills have been identified as one of the possible sources of PBDEs in the environment. Meanwhile, the unprecedented economic and population growths of some Asian countries over the last decade have led to significant inc...

Plastic resin pellets collected from remote islands in the Pacific, Atlantic, and Indian Oceans and the Caribbean Sea were analyzed for polychlorinated biphenyls (PCBs), dichloro-diphenyltrichloroethane and its degradation products (DDTs), and hexachlorocyclohexanes (HCHs). Concentrations of PCBs (sum of 13 congeners) in the pellets were 0.1-9.9 ng...

To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and i...

Trace metal levels in bottom sediments of Laguna Lake (Luzon, Philippines) and of five of its tributary rivers, and in lakeshore samples were compared. Total metal analyses by flame atomic absorption spectrophotometry indicate relatively low (Cu, Zn, and Pb) to moderate (Fe, Mn, Hg, and Cd) metal contamination in the sediments.