Water Quality

Dioxins (dioxins and furans)

Dioxins and furans are unintended by-products of industrial and natural combustion processes occurring between 250°C and 450°C. They can also be generated from burning of domestic waste, forest fires, vehicle emissions and tobacco smoke.

Trace levels of dioxins and furans were detected in raw sewage, sewage effluent, river waters as well as marine water samples in Hong Kong. Nevertheless, these levels were generally below the standards of both the USEPA and Japan for protection of aquatic life in marine water. The average levels of dioxins and furans in marine sediments were low and comparable with many harbours and coastal areas in the world, such as Tokyo Bay, Spanish coast, Osaka Bay, San Francisco Bay, Pearl River Delta and Sydney Harbour. The levels of dioxins and furans in most biota samples including fish, shrimps and bivalves were low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Polychlorinated biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) comprise over 200 individual compounds (or congeners) of varying toxicity. In the 70s, PCBs were widely used in capacitors, transformers, plasticizers, ink, adhesives and carbonless duplicating paper. In the 80s, PCBs were no longer used in the production of capacitors and transformers, and PCBs-containing equipment was phased out in Hong Kong. It is known that PCBs contaminants are generally bound to soil and sediments and may be released to the water slowly over a long time.

A total of 18 PCB congeners listed in Appendix A of the Works Bureau Technical Circular (Works) No. 34/2002 Management of Dredged / Excavated Sediment were tested in the programme and they were not detected in the marine water samples or discharges from potential pollution sources. Although some PCBs were found in marine sediments in central Victoria Harbour, their levels were generally lower as compared with those in the nearby Pearl River Estuary. In terms of biota, the levels of PCBs in most biological samples were low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Dichlorodiphenyltrichloroethane (DDT)

DDT was widely used as insecticides in agricultural, residential and commercial applications before the 1980s. DDT was banned (deregistered) in Hong Kong since 1987. The use of DDT as an additive to antifouling paint was also banned in 2009 in the Mainland.

The monitoring data show that DDT was at a level below the reporting limits in marine water or stormwater runoff samples. Very low levels of DDT were occasionally present in some sewage effluent and river water samples and these levels were, moreover, well below the US standard for protection of aquatic life. The levels in marine sediments in Hong Kong were also generally low and meet the relevant US standard for protection of benthic organisms, apart from the some samples collected in Tolo Harbour in earlier years of the programme. In marine biota samples, the DDT levels in all biota samples were also very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Aldrin

Aldrin has been widely used for controlling soil insects and certain insect vectors of disease. The use of aldrin has been banned in Hong Kong since 1988.

The monitoring of aldrin started in 2007 and it was generally not detected in the marine water, river water, river sediment, stormwater runoff, sewage effluent and sewage sludge samples collected. While low levels of aldrin were occasionally found in marine sediments, they were below the US standard for protection of benthic organisms. In marine biota, the levels were also very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Chlordane

Chlordane had been used as insecticides for fire ant control, on lawns, and on a variety of crops. The use of chlordane was banned in Hong Kong since 1991.

Similar to aldrin, the monitoring of chlordane began in 2007 and it was generally not detected in the marine water, river water, stormwater runoff and sewage effluent samples collected so far. Only trace levels were occasionally detected in marine sediments, river sediments and sewage sludge but their levels met the US standards for protection of benthic organisms. In marine biota, trace levels were detected in some species but the levels were very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Dieldrin

Dieldrin had been used as insecticides on fruit, soil and seed to control tsetse flies and other vectors of tropical diseases. The use of dieldrin was banned in Hong Kong since 1988.

The monitoring of dieldrin started in 2007 and it was generally not detected in the marine water, river water, stormwater runoff and sewage effluent samples collected. Only trace levels were occasionally detected in marine and river sediments, and sewage sludge but their levels were lower than the US standards for protection of benthic organisms. In marine biota, the levels were also very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Endrin

Endrin has been used as a rodenticide to control mice and voles, as well as an insecticide used on cotton, rice, and maize. Endrin is not a registered pesticide and not permitted to be used in Hong Kong.

The monitoring of endrin started in 2007 and it was generally not detected in the marine water, river water, river sediment, stormwater runoff, sewage effluent and sewage sludge. A trace level of endrin was detected in one marine sediment sample but the level was lower than the Canadian sediment guideline for protection of aquatic life. The level of endrin in marine biota samples was very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Heptachlor

Heptachlor is a termiticide and an insecticide used on seed grain and crops. It has also been used extensively for fire ant control, and is present as an impurity in the pesticide chlordane. Heptachlor is not a registered pesticide in Hong Kong.

The monitoring of heptachlor started in 2007 and it was generally not detected in the marine water, river water, river sediment, stormwater runoff, sewage effluent, sewage sludge and marine biota samples collected. Trace levels were occasionally detected in marine sediment but they all met the US standard for protection of benthic organisms.

Hexachlorobenzene

Hexachlorobenzene (HCB) is a fungicide formerly used as a seed treatment, especially on wheat. HCB is not a registered fungicide in Hong Kong.

The monitoring of HCB started in 2007 and it was generally not detected in the marine water, river water, stormwater runoff and sewage effluent samples collected. However, trace levels were occasionally detected in marine sediments, river sediments and sewage sludge but their levels were lower than the US standards for protection of benthic organisms. The level in marine biota was very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Mirex

Mirex is an insecticide which was popularized to control fire ants in the past. The use of mirex was banned in Hong Kong since 1997.

The monitoring of mirex started in 2007 and it was generally not detected in the marine water, river water, stormwater runoff and sewage effluent samples collected so far. Trace levels were occasionally detected in marine sediments and river sediments but the levels were lower than the US standards for protection of benthic organisms. In marine biota, trace levels were occasionally detected in some species but the levels were very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Toxaphene

Toxaphene is an insecticide and was used in the cotton and soybean growing areas in the past. The use of toxaphene was banned in Hong Kong since 1984.

The monitoring of Toxaphene bagan in 2007 and its level was very low and below detection limit in nearly all environmental, biota and land-based source samples analysed.

Chlordecone

Chlordecone is a synthetic chlorinated organic compound mainly used as an agricultural pesticide. It is not a registered pesticide in Hong Kong. It is one of the new POPs listed under the Stockholm Convention in 2009.

Monitoring of Chlordecone began in 2011 and its levels are generally below the reporting limits for marine water, marine sediment, river water, river sediment, stormwater runoff, sewage effluent and sewage sludge samples. The level in biota samples was very low and would pose negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Pentachlorobenzene

Pentachlorobenzene was used in PCB products, in dyestuff carriers, as a fungicide and a flame retardant. It also present as impurities in products such as solvents or pesticides. It is one of the new POPs listed under the Stockholm Convention in 2009.

Monitoring of pentachlorobenzene began in 2011 and its levels are generally below the reporting limits for environmental, biota and land-based source samples monitored.

Perfluorooctane sulfonic acid

Perfluorooctane sulfonic acid is intentionally produced and an unintended degradation product of related anthropogenic chemicals. The current intentional use is widespread and includes: electric and electronic parts, fire-fighting foam, photo imaging, hydraulic fluids and textiles. It is one of the new POPs listed under the Stockholm Convention in 2009.

Monitoring of PFOS began in 2011 and its levels are generally below the reporting limits for marine water, marine sediment, river sediment and biota samples. Only trace levels were occasionally found in river water, sewage effluents, stormwater runoff and sewage sludge.

Hexachlorocyclohexanes (HCHs)

Four Hexachlorocyclohexanes (HCHs) congeners, namely alpha-HCH, beta-HCH, gamma-HCH (also named as Lindane) and delta-HCH have been included in the monitoring programme since 2004. HCHs are effective insecticide for animal ectoparasites, soil insects and other disease organisms. HCHs were banned (deregistered) in Hong Kong in 1991.

Alpha-HCH, beta-HCH and gamma-HCH were generally at levels below their reporting limits in the marine water, river water, stormwater runoff and sewage effluent samples. Levels in sludge samples were also very low except those for SCISTW which occasionally had higher levels of beta and gamma HCH. Nevertheless, the levels of alpha-HCH, beta-HCH, gamma-HCH in marine, and river sediments were very low and far below the US standards for protection of benthic organisms for these three chemicals. In addition, the levels in marine sediments were also generally comparable with the levels in East China Sea and north South China Sea, and lower than those in the Pearl River Estuary and Yellow Sea. The levels of HCHs in biota samples were very low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Tributyltin

Tributyltin (TBT) is an organotin compound used in antifouling paints since the 1970s to prevent the growth of fouling organisms on ships. TBT leaches from paint and accumulates in the sediment of harbours and ports. All TBT pesticides are controlled under the Pesticides Ordinance (Cap. 133) and no permit has been issued by the Agriculture, Fisheries and Conservation Department for the local use of TBT containing antifouling paints since 2006.

TBT was generally at levels below the reporting limits for marine water, river water, sewage effluent or stormwater runoff samples. The levels of TBT in Hong Kong marine sediments mostly met Australia‘s sediment quality guideline for the protection of benthic organisms and were generally within the range (falling on the low-side) reported in other Asian countries, i.e. Japan, Vietnam and Malaysia. The levels of TBT in the biota species were low and largely comparable with the levels for biota in the Pearl River Estuary area and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Polycyclic aromatic hydrocarbons (PAHs)

The sources of PAHs in the environment are diverse, including cigarette smoke, vehicle exhaust, grilling of meat, coal burning and hazardous waste sites. There are more than 100 PAH compounds known. The EPD’s Toxic Substances Monitoring Programme monitors 16 of the more toxic PAH compounds, namely acenaphthene, acenaphthylene, anthracene, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene, chrysene, dibenzo(ah)anthracene, fluoranthene, fluorene, indeno(123-cd)pyrene, naphthalene, phenanthrene and pyrene.

The monitoring results show that the 16 PAHs tested were generally not found in the marine water and land based effluent discharge samples. In marine sediments, the PAHs levels were also low and were generally lower than those reported in the Pearl River Estuary, Macau, Jiaozhou Bay and Singapore. Benzo(a)pyrene is used as a biomarker for carcinogenic PAHs in marine biota and its level in local biota were low and posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Phenol, Nonylphenol and Nonylphenol ethoxylates

Phenol is commonly found in phenolic resins used in the plywood, construction, automotive and appliance industries. It is also used as antiseptics in ear and nose drops, throat lozenges and mouthwashes. Nonylphenol ethoxylates occur in a variety of residential and commercial cleansing products such as detergents, shampoo and surface cleaners. Nonylphenol is often found in wastewater treatment plant effluent as a breakdown product from NP ethoxylates in surfactants and detergents.

Phenol was generally at levels below the reporting limits in marine water and river water samples. However low levels were found in stormwater runoff and sewage effluent samples but they all met the relevant US standard. For marine sediments, phenol was occasionally detected only in Deep Bay.

Nonylphenol was detected in most of the marine and river water samples as well as storm runoff samples but they were all below relevant US criteria for protection of aquatic life in marine as well as fresh water. Higher levels of nonylphenol were detected in raw sewage and effluent samples from sewage treatment works which suggested that they were the likely sources of this chemcial in Hong Kong marine waters. On the other hand, the levels of nonylphenol in all marine sediment samples collected so far met the US standard for protection of benthic organisms except for Deep Bay, Victoria Harbour and inner Tolo Harbour.

Similar to nonylphenol, trace levels of nonylphenol ethoxyates were detected in marine water, marine sediment, river water, stormwater runoff, sewage treatment works’ effluent and raw sewage samples in Hong Kong.

Polybrominated diphenyl ethers (PBDEs)

Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in plastics, polyurethane foams and textiles since 1970s. There are three main types of PBDEs: penta- (five), octa- (eight) and deca- (ten) BDE present in the environment. The use of penta and octa PBDEs was banned by the European Union in 2004.

PBDEs were first monitored in marine sediments in 2005, and more analyses have subsequently been added since 2007 to include marine water, river sediment, biota and potential land-based sources samples. Trace levels of comm. penta-BDE and comm. octa-BDE were occasionally detected in marine water, marine sediment, stormwater runoff, sewage effluent, sewage sludge, river water and sediment as well as marine biota samples collected. However, these levels were all below the relevant standards of the European Union. The low levels in biota posed negligible lifetime health risk to human due to consumption of marine biota in daily life^***.

Hexabromobiphenyl (HBB)

Hexabromobiphenyl belongs to a wider group of chemical called polybrominated biphenyls (PBBs). HBB was used in North America as a fire retardant in commercial products such as business machine and motor housings, radio and TV parts as well as polyurethane foam for auto upholstery. Hexabromobiphenyl was added to the POPs list of the Stockholm Convention in 2009.

The monitoring of HBB started in 2007 and its levels were generally below the reporting limits for marine water, river water, stormwater runoff, sewage effluent and marine biota samples. Nevertheless, trace level were detected in one marine sediments, river sediments and sewage sludge samples. We will continue to closely monitor this chemical in the local environment.

Methyl Mercury

Methyl mercury is the most common form of organic mercury. It can be generated from natural processes and human activities, including power generation, industrial discharges and waste disposal. In the atmosphere, land and water, metallic mercury undergoes complex chemical reactions to form methyl mercury.

The levels of methyl mercury in local biota samples were well within the Mainland and US food standards.

Non-metallic inorganic - Fluoride

Inorganic fluorides are released naturally in the weathering of minerals and volcanic eruption. Anthropogenic sources of fluorides include: industrial processes such as aluminum smelting, steel production, manufacturing of ceramics, glues, adhesives and fluoridation of drinking water.

Since 2004, fluoride was found commonly in marine sediment samples and within the range of between 4 – 18 mg/kg dry weight. Higher concentrations of fluoride were generally found in the sediments of central Victoria Harbour, which may be related to the discharges of the sewage screening plants or urban runoff.