环境风险评价

Hazard Assessment of Western Baltic region1 IntroductionThe Baltic Sea is a semi-closed sea of about 415,000 Km2. As a matter of fact, the Baltic Sea has been characterized by the interaction of fresh and saltwater sources. However, some issues caused by toxicity due to the development of industries can not be avoided. The environmental situation has deteriorated since the industrial and agricultural waste including some toxic, which may can not be easily degraded. These toxics deposit and accumulate in the aquatic environment, then even deposit in biological bodies by bioaccumulation via food chain.. Some of these substances are highly toxic, while some are not that toxic but will also cause damage to ecological health in a long time. In the matter of this fact, organisms and even human’ s heal th are on the hazard. So the meaning of hazard risk assessment is important. A hazard assessment needs to consider the physical-chemical, toxicological and ecological properties of a chemical substance and the result of this assessment leads to Classificat ion with assignment of ‘R Phrases’; however, this does not reflect the risk of the materials to workers, consumers or the environment and to take the hazard data to the next stage of assessment, it is necessary to understand potential exposure.In our case, we focus on the historical exposure and effects associated with polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) ,dioxin-like polychlorinated biphenyls (DL-PCBs) and brominated flame retardants(PBDE-47,PBDE-99,PBDE-209). Generally these toxicity can cause problems in nervous system and blood circulation system, and also especially have serious effect on the function of livers and lungs. In addition, they can also inhibit the growth of fetuses.2Physical –Chemical properties of toxicities2.1 PCDD/FsPCDD PCDFIn general, PCDD/Fs are non-polar, hydrophobic, lipophilic and stable chemicals, although their properties vary with degree of chlorination. They are stable in the presence of strong acids and bases and are stable at very high temperatures. Solubility in water decreases over several orders of magnitude with increasing chlorination. Their octanol-water partition coefficients (log Kow) increase with chlorination andare among the highest measured for environmental organic contaminants. Changes in properties with chlorination/molecular mass, result in an increased tendency to partition into soils and sediments and to the particulate phase of air and water. Melting points and predicted boiling points of PCDD/Fs from B.Rordorf [1989] are given in Table 1.Estimated temperature dependencies are given in Table 2.Temperature dependencies of PCDD/Fs vapor pressure derived from these estimates are given in Table 3.Temperature dependencies of Henry law constant for PCDD/Fs are given in Table 4.2.2 DL-PCBsDL-PCBsPolychlorinated biphenyls or PCBs are a group of extremely stable aromatic chlorinated compounds which, like dioxins, are relatively resistant to biological degradation and hence persist and accumulate in the environment and in the food chain. There are 209 structurally possible PCB compounds (congeners), with one to ten chlorine atoms per molecule. They have excellent electrical and heat transfer properties, which led to their widespread use in a variety of industrial, commercial and domestic applications. Some poly-chlorinated biphenyls (PCBs) are called dioxin-like PCBs (DL-PCBs) because they have a structure very similar to that of dioxins and have dioxin-like effects.Some toxicologic parameters are in table 5.Basic chemical and physical data are in table 6.2.3 PBDEsPBDEsPBDEs are highly water insoluble, hydrophobic substances. Commercial penta BDE is a viscous liquid, but pure congeners and the other commercial products are solids at room temperature. PBDEs are semivolatile compounds with low vapour pressure and low water solubility. In the air, they exist in the gaseous phase and in the particulate phase. Due to the low vapour pressure they tend to be strongly attracted to air particles, but the amount actually associated with particles is dependent on temperature, particle size and of course, particle concentration. Generally, a greater amount exist in the gaseous phase during warm periods than during cold periods,because of the temperature dependence of the physical-chemical properties. In aquatic environments, PBDEs mainly become attracted by particles, because of the low water solubility.Physical-chemical properties of PBDE-47, PBDE-99, PBDE-209 are in table 7.3.Toxicity bioaccumulation and hazard risk assessment3.1 Toxicity bioaccumulation3.1.1Mobility, fate and transport of PCDD/Fs in the environmentMobility of PCDD/Fs is extremely low since it has a very low solubility in water and high adsorption capability. Therefore PCDD/Fs always accumulate in fatty tissue in biological body. The air-vegetation-livestock-human pathway is probably the most important route of human exposure.Accumulation of PCDD/Fs in the food chain is a consequence of their solubility in fats. Bioaccumulation is high in fish as well as in fat and in the liver of terrestrial organisms. However, accumulation in plants is moderate. The main route of PCDD/Fs to vegetation is via direct deposition from the atmosphere. PCDD/Fs is mainly the by-product of the industrial process, but it also widely exists in the nature in a normal low concentration because of some natural processes, such as volcanic eruptions and forest fires. PCDD/Fs are harmful by-productions from metallurgy, chlorine bleaching and pesticide manufacture industries. The most reprehensible problem harming environment is from waste incinerations, such as solid waste and medical waste incineration. The problem is mainly caused by insufficient combustion.Although the mobility of PCDD/Fs incorporated into sediment is thought to be minimal, there is evidence from laboratory studies that transformation of PCDD/Fs via reductive dechlorination can occur. The dechlorination process is expected to be much slower in the environment however. Soil, along with sediment, is the ultimate destination for PCDD/Fs. Once PCDD/Fs have been deposited to soil there is very little transformation or movement and estimated half-lives for PCDD/Fs in soil are decades. After PCDD/Fs entre the atmosphere, they will be transported by advective process. Most of PCDD/Fs may be deposited from the atmosphere to the ground, vegetated and water surfaces by three processes:1)Dry deposition of gases and particles, which means it directly interact between the atmosphere and the ground.2)Wet deposition. It comes down companying with falling hydrometeors.3)Occult deposition. It exists in fog droplets which do not fall under gravity because of their small size)3.1.2 Mobility, fate and transport of DL-PCBs in the environmentAccumulation in humus layer with little mobility; following sorption, mobility by way of vapor phase. There is very little degradation; the persistence increases with the degree of chlorination.Moreover, due to their chemical stability and persistence, PCBs could be globally distributed by the movement of water, atmosphere, and food cycle. Once in the environment, PCBs are highly resistant to chemical and biological degradation. PCBs, particularly the highly chlorinated ones, have been known to persist in water soils, sediment and biota for long periods of time.Although PCBs have low solubility in water, the immense amount of water in the oceans is still capable of holding a significant quantity of PCBs. In water, PCBs can be existed in the form of either truly dissolved or adsorbed suspended particles. Due to the presence of suspended particles with adsorbed PCBs, the amount of PCBs in water can sometimes exceed than what theoretically expected from the PCB's water solubility. Furthermore, the presence of human waste and dissolved organic carbon in water could also enhance the solubility of PCBs. The transport of PCBs in oceans is mainly due to the ocean current, and the ocean current between continents could easily transport PCBs from one country to another country.3.1.3 Mobility, fate and transport of PBDEs in the environmentThe environmental patterns of PBDEs in the air vary from the patterns in soil, sediment, and sludge. PBDEs strongly adsorb to these matrixes, and the congener patterns tend to reflect those in the commercial mixtures, except in sludge.Biodegradation is not an important pathway for the PBDEs, but photolysis possibly plays an important role in their transformation. When PBDEs existing in biological fat exposure in sunlight, more potentially toxic and more bioavailable with lower brominated will form. Due to the uncertainty in vapour pressure, the results obtained for BDE 209 possibly differ from the actual truth. Adopting a lower vapour pressure yields a higher amount partitioning to aerosols, which also increases the deposition of this chemical and thus the concentration in soil, urban film and sediment. Due to the large surface area of water, increased deposition also shifts the relativedistribution from soil to sediment, resulting in a higher percentage residing in sediment and a lower in soil.3.2 Toxicological hazard to organisms in the aquatic environment (ecological health)3.2.1 PCDD/FsAquatic environment, as the most important ecology environment, plays the key role in accumulation of PCDD/Fs. As presented in the fig.1, PCDD/Fs in the fresh water has a growing accumulated concentration before 1980 and then decreases. This situation may caused by the fact that the organisms such like zooplankton and fish in the water exposes in such aquatic environment and then deposit toxicities by eating. But fortunately, from the data we got from CoZMoMAN, we can figure that the highest concentration is only 1.99E-17 g/m3, which will only cause slight even no damage to organisms in the water. But the concentration in fish and zooplankton is much higher. From the figure4.1, we can know that the concentrations in organisms changes widely from 0 to 0.015 as different ages. The more mature organism accumulate more toxicity, absolutely supper more from the damage.3.2.2 DL-PCBsFish and other seafood are the main contributors to total TEQ intake from DL-PCBs. However, those individuals in some groups of organisms, which frequently consume high quantities of certain species , could significantly increase their DL-PCB intakes. Their environmental persistency, bioaccumulation and toxicological effects could be potentially similar to those of PCDD/Fs. We can know from fig.2, the concentration in fresh water and sediment both increase to the peak when 1975 and goes down afterwards. The sediment concentration increase as a result of the sedimentation of the toxicity.And the reduction may be contributed to ingestion and adsorption by organisms in the water. Although the peak number 2.66E-13 ng/g and 9.32E-13 ng/g are ignorable, we can also know from the data(fig4.2) that the peak of concentration in organisms in the water is relatively high, especially in 9-10 years herrings fat of 0.015ng/g. In this fact, fish and zooplankton are on hazard of PCBs, getting worse as the exposure time extents.3.2.3 PBDEsFrom the figure3, it can be obvious that the trend of concentrations on fresh water and sediment are mostly same. This phenomenon can due to the sedimentation and ingestion. Toxicities continuously settle into the bottom as small particle and those in the seawater are intaken by fish and zooplankton. Then toxicities concentrate and accumulate in fat in a much higher concentration.At the same time, by comparing with the data from CoZMoMAN, as figure(4.3-4.5), the accumulation in fish and zooplankton obviously concentrated and may cause significant effect on to different ages of organisms’ health . Effects of PBDEs have been reported in algae, invertebrates and in fish. In fish, fatty liver and reduced spawning are the main consequence.3.3 toxicological hazard to humans (human health)Comparing toxic accumulation concentration with LD50 of mouse. As the safety factor of human is 1000, LD50 (human)=LD50(mouse)/1000.3.3.1 PCDD/FsIn this case, TDLo of PCDD/Fs is 0.1 mg/kg. In the figure5.1, we can find that the concentration in humans is at most 0.035ng/g , which means that accumulation in human body is far below the damaging concentration. However, the effect of PCDD/Fs should not be ignore if humans are exposed in PCDD/Fs for a very longtime. Long time exposure may cause damage of the immune system, development of the nervous system, endocrine system and reproductive function. Chronic exposure to dioxins has lead to several types of cancer in animals. The growing fetus are the most sensitive group with PCDD/Fs. The growth of organ system can be effected, too. If humans shortly exposure to high levels of dioxins, they may have skin lesions, such as acne and skin discoloration. PCBB/Fs can also cause alteration of liver functions.3.3.2 DL-PCBsThe less serious concentration of long-evans rat is 1mg/kg, so the value for human is nearly 1ng/g . This value is also much higher than the peaks of graphs(fig 5.2) which presents DL- PCBs concentration in man and female human bodies. This fact may caused by their extremely stable chemical property and high sedimentation rate in the sea. Thus this kind of toxicity can be mostly tested in aquatic environment and fish fat. However, PCBs are generally regarded as having potential to cause adverse effects on health, with particular concern being expressed about the 12 so-calleddioxin-like PCBs. This group of non-ortho (PCB 77, 81, 126, 169) and mono-ortho (PCBs 105, 114, 118, 123, 156, 157, 167, 189) PCBs are assumed to have essentially the same toxicity potential as the dioxins and furans. It can be observed that human from 40-50 ages have much more concentrations than other age groups. People intake even low concentrations of DL-PCBs, also can be damaged because of its long life-time and low metabolism rate. Serious poisoning caused by PCB can bring out diarrhea, ataxia, inhibition of central nerves, etc, and even death. Toxic of PCB depends on animal species, sex, spread path, chemical structure of the PCB itself, and the different impurities. Human is probably one of the most sensitive species. PCBs can be easily intaken by humans via gastrointestinal tract, lungs, and skin. After entre human body, PCBs widely spread to the hole body, and mostly deposit in liver and fat. PCB in the matrix can transfer to the fetus via the placenta, and PCB in the fetal liver tend to be higher than the tissue of mothers. So damage to fetus are even more serious than adults. The contribution from dietary changes of young women, which may partly explain the more rapidly decreasing trend of DL-PCB concentrations in humans.3.3.3 PBDEsAccording to the data and figures(fig5.3-5.5) about the concentrations in human body, we can know that the concentration of PBDE-209 kept increasing by now, and there is no decreasing trend. Thus, we can infer that the PBDEs concentration can continue to increase and there is a possibility that it can exceed the less serious damaging concentration and cause damage to human health. Whereas, the concentration of PBDE-47 and PBDE-209 reach the peak in 2005 and then tend to decrease due to the high metabolism rate. Young people are under more risk of being damaged by toxicities. Very serious health effects are associated with exposure to PBDEs, but toxicity depends on the compound and the amount that one is exposed to. PBDEs are chemically similar to PCBs and, not surprisingly, they show similar health effects as well. They are biomagnified toxic compounds, meaning they accumulate within food chains. In contrast to penta-BDE, deca-BDE is poorly absorbed which may limit its potential toxicity. Toxicity testing indicates that PBDEs may cause liver, thyroid, and neuro developmental toxicity .There is also a study showing that exposure to very high doses of deca-BDE can cause tumors.4 ConclusionAccording to the risk assessment results, we can get conclusions blow:●In the bioaccumulation system, toxicity concentration in aquatic organisms are much higher than those in human bodies. Therefore hazard risk in aquatic environment is regarded under more risk.●Although most of the accumulation concentrations haven’t exceeded the damaging concentration, long time exposure will also have toxicological hazard to organisms in The aquatic environment and humans.●Damages caused by these organic toxicity mainly effect on nervous system, blood circulation system,development of organisms and functions of visceral organ.Table1. Melting and boiling points of PCDD/FsTable 2. Solubility of PCCD/Fs in water as a function of temperatureTable 3.Temperature dependence of vapor pressure of PCCD/FsTable 4.Temperature dependencies of Henry law constant for PCDD/FsTable 5. Parameters of PCBsTable 6. Basic chemical and physical dataTable 7.Physical-chemical properties of PBDE-47, PBDE-99, PBDE-209Figure 1. concentration of PCDD/Fs in ng/gPOCfresh water concentration of PCDD/Fs in ng/gPOC sediment concentration in PCDD/Fs ng/gPOCFigure 2 concentrations of DL-PCBsFreshwater con of DL-PCBs Sediment con of DL-PCBsFig 3. Concentration of PBDEsFresh water con of PBDE-47 Sediment con of PBDE-47Fresh water con of PBDE-99 Sediment con of PBDE-99Fresh water con of PBDE-209 Sediment con of PBDE-209Figure 4. 1PCDD/Fs of aquatic organisms （ng/g）Figure 4. 2 DL-PCBs of aquatic organisms （ng/g）Figure 4.3 PBDE-47 of aquatic organisms （ng/g）Figure 4.4 PBDE-99 of aquatic organisms （ng/g）Figure 4.5 PBDE-209 of aquatic organisms（ng/g）、Figure 5. 1 PCDD/Fs of humans （ng/g）Figure 5. 2 DL-PCBs of hunmans （ng/g）Figure 5.3 PBDE-47 of humans（ng/g）Figure 5.4 PBDE-99 of humans （ng/g）Figure 5.5 PBDE-209 of humans (ng/g)。