Hazardous Air Pollutants
Introduction
This
section includes pollutants singled out for control under recent international
protocols extending the Convention on Long-range Transboundary Air
Pollution- namely Persistent Organic Pollutants (POPs) and Heavy Metals (HMs).
UN/ECE Heavy Metals and POPs Protocols
The Convention on Long-range Transboundary Air Pollution was signed in 1979 and entered into force in 1983. Since its entry into force the Convention has been extended by a number of protocols, including the 1998 Protocol on Heavy Metals and the 1998 Protocol on POPs. These two Protocols are given in outline below; more information may be found at the UN/ECE web site, located at:- http://www.unece.org/env/lrtap/. The UK has signed both of these protocols but they have not yet been ratified by a sufficient number of countries to come into force.
Persistent Organic Pollutants (POPs)
The UN/ECE
Protocol on Persistent Organic Pollutants focuses on a list of 16 substances
(or groups of substances), which have been identified according to certain risk
criteria. In brief, these 16 pollutants may be classified in three source
sectors as follows:
1. Pesticides:
aldrin, chlordane, chlordecone, DDT, dieldrin, endrin, heptachlor,
hexachlorobenzene (HCB), mirex, toxaphene, hexachlorocyclohexane (HCH) (incl.
lindane);
2. Industrial Chemicals: hexabromobiphenyl, polychlorinated biphenyls (PCBs);
3. By-products or Contaminants: dioxins, furans, polycyclic aromatic hydrocarbons (PAHs).
The
ultimate objective of the protocol is to eliminate any losses, discharges and
emissions of POPs to the environment. This is achieved through several
different legislative mechanisms. First, the production and use of several
compounds is banned (aldrin, chlordane, chlordecone, dieldrin, endrin,
hexabromobiphenyl, mirex and toxaphene). Secondly, several compounds are
scheduled for elimination at a later date (DDT, heptachlor, hexachlorobenzene,
PCBs). Finally, the protocol severely restricts the use of selected compounds
(DDT, HCH- including lindane and PCBs). Limited uses which are thought to be essential
and for which there are no adequate substitutes, can be exempted. For instance,
the use of substances like DDT would be allowed under the protocol for
public health emergencies. The protocol includes provisions for dealing
with the surplus of products that will be banned.
Under the
protocol, countries are also required to reduce their emissions of dioxins,
furans, PAHs and HCB below their levels in 1990 (or an alternative year between
1985 and 1995). The protocol requires the best available techniques (BAT) to be
applied to cut emissions of these POPs. For the incineration
of municipal, hazardous and medical waste, it lays down specific limit values.
The protocol allows for the addition of further compounds into control,
depending on the development of the scientific basis for such an action.
In 1999 EPAQS published a report on PAHs which recommended an Air Quality Standard of 0.25 ng m-3 benzo[a]pyrene as an annual average. As a result, further work assessing the concentrations of PAHs in the atmosphere has been commissioned by Defra and the results compared with the spatially disaggregated emissions inventory.
In August 2002 PAHs were added to the list of pollutants covered by the Air Quality Strategy for England (see Chapter), and an objective was set relating to the PAH concentrations in the air. As a consequence there is a continued drive to decrease PAH emissions from the major sources.
Continued improvements have been made in compiling the 2000 UK emission estimates for POPs. This has been instigated in a response to the increasing interest in hazardous air pollutants and their impact on the environment over the last several years. The level of data available for many of these pollutants is relatively limited and hence several areas of the current emission inventory have been targeted for improvements which will be included in future emission estimates as a part of the NAEI continuous improvement process.
Table 6.1 lists the toxic pollutants (i.e. POPs and heavy metals) included in the current inventory together with their total UK emissions in 2000. Each of the pollutant classes are considered in more detail in the following sections.
Heavy Metals
The UN/ECE
Protocol on Heavy Metals targets three particularly harmful substances: lead,
cadmium and mercury. Countries are obliged to reduce their emissions of these
three metals below their levels in 1990 (or an alternative year between 1985
and 1995). The protocol aims to cut emissions from industrial sources (iron and
steel industry, non-ferrous metal industry), combustion processes (power
generation, road transport) and waste incineration.
The
protocol specifies limit values for emissions from stationary sources and
requires BAT for obtaining emission reductions from these sources, such as
special filters or scrubbers for combustion sources or mercury-free
processes. The protocol also requires countries to phase out leaded petrol.
Under the
protocol, measures are introduced to lower heavy metal emissions from other products e.g.
mercury in batteries, and examples are given of management measures for other
mercury-containing products, such as electrical components (thermostats,
switches), measuring devices (thermometers, manometers, barometers),
fluorescent lamps, dental amalgam, pesticides and paint.
Further
metals may be added to the protocol, and further measures may be introduced for
lead, cadmium and mercury, depending on the development of the scientific basis
for action.
The best
known effects of heavy metals are those on humans and animals. Of these, the most important effects are
deterioration of the immune system, the metabolic system and the nervous
system. They lead to disturbances in behaviour and some heavy metals are suspected
to be or have been proven to be carcinogenic.
The impact
of heavy metals on the environment due to long-range transport can be
summarized as:
1. Impact on aquatic ecosystems.
Atmospheric deposition of metals may influence the quality of surface waters
and ground water. In addition to the
effects on the uses of water (e.g. restricted use of water for human
consumption, livestock, recreation etc) accumulation in aquatic organisms may
have adverse effects on the food web.
2. Impact on terrestrial systems. Metal uptake by plants is a key route for
the entry of metals into the food chain.
Contaminants may be toxic to plants and can alter the structure or
diversity of a habitat. When plants
accumulate metals, these can be ingested by animals creating the potential for
toxic effects at higher trophic levels.
3. Mesofauna and macrofauna. The accumulation of cadmium and lead in
birds and mammals in remote areas is attributable to long range atmospheric
transport.
4. Agricultural products. Airborne heavy metals account for
significant fractions of the total heavy metal input to arable soils.
Major environmental problems due to long range transport have been
reported, relating to the:
·
Accumulation
of Pb, Cd and Hg in forest top soils, implying disturbed nutrient
recirculation in forest ecosystems and
increased stress on tree vitality in central Europe, reinforced by the
acidification of soils
·
Highly
increased content of Hg in fish from lakes, especially in Scandinavia.
Table 6.1 Total UK
Emissions of Toxic Pollutants
|
Pollutant |
Total 2000 UK emission |
|
|
Persistent organic
compounds (POPs) · Polycyclic aromatic hydrocarbons (PAHs) |
2165 |
tonnes (USEPA16) |
|
· Dioxins
and Furans (PCDD/F) |
347 |
TEQ grammes |
|
· Polychlorinated
biphenyls (PCBs) |
1.71 |
tonnes |
|
· Pesticides |
|
tonnes |
|
- lindane (g-HCH) - pentachlorophenol (PCP) - hexachlorobenzene (HCB) |
32 476 0.79 |
|
|
· Short Chain Chlorinated Paraffins (SCCPs) |
3 |
tonnes |
|
· Polychlorinated Napthalenes (PCNs) |
NE1 |
|
|
· Polybrominated Diphenyl Ethers (PBDEs) |
13.8 |
tonnes |
|
|
tonnes |
|
|
· Arsenic |
35 |
|
|
· Beryllium |
16 |
|
|
· Cadmium |
5.2 |
|
|
· Chromium |
63 |
|
|
· Copper |
46 |
|
|
· Lead |
496 |
|
|
· Manganese |
303 |
|
|
· Mercury |
8.5 |
|
|
· Nickel |
115 |
|
|
· Selenium |
50 |
|
|
· Tin |
74 |
|
|
· Vanadium |
157 |
|
|
· Zinc |
336 |
|
1NE- Not Estimated. It has not been possible to make an emission estimate
Persistent organic pollutants
Persistent organic pollutants (POPs) are found in trace quantities in all areas of the environment. They accumulate in humans and plants, and have differing degrees of toxicity. POPs do not readily break down in the environment with half-lives in soils in the order of years, although they may be transformed both physically and chemically over long periods.
Over recent years there has been a growing interest in these pollutants and in particular their potential chronic toxicity and impacts on human health. This is reflected by the recent international agreement to reduce releases of these chemicals under the UN/ECE Persistent Organic Pollutants Protocol (detailed in Section 6.1) and their consideration for air quality standards by the Expert Panel on Air Quality Standards (EPAQS). The detailed methodology for the compilation of these inventories depends on the combination of emission factors gathered from a range of sources and production statistics used elsewhere in the emission inventory or developed for the specific sector concerned.
The UK NAEI does not include
emission estimates for a number of POPs that have been banned in the UK for several years. Table 6.2 below indicates
the years in which the use of particular POPs were banned or their use severely
restricted, and whether the listed POPs are included in the NAEI.
Table 6.2 POPs Included/Not
Included in the NAEI and Corresponding Year of Ban on Use
|
Compound or Compound Group |
Banned in UK |
Included in NAEI |
|
Polycyclic aromatic hydrocarbons
(PAHs) |
- |
Yes |
|
Dioxins and Furans
(PCDD/Fs) |
- |
Yes |
|
Polychlorinated
biphenyls (PCBs) |
- |
Yes |
|
Hexabromobiphenyl |
Never Used |
No |
|
|
|
|
|
Pesticides |
|
|
|
g-Hexachlorocyclohexane |
- |
Yes |
|
Pentachlorophenol1 |
19952 |
Yes |
|
Hexachlorobenzene1 |
1975 |
Yes |
|
Aldrin |
1989 |
No |
|
Chlordane |
1992 |
No |
|
Dichlorodiphenyl-trichloroethane
(DDT) |
1984 |
No |
|
Chlordecone |
1977 |
No |
|
Dieldrin |
1989 |
No |
|
Endrin |
1984 |
No |
|
Heptachlor |
1981 |
No |
|
Mirex |
Never Used |
No |
|
Toxaphene |
Never Used |
No |
1Hexachlorobenzene
and pentachlorophenol are also emitted from other sources as well as being or
having been active ingredients in pesticides.
2 Use of
pentachlorophenol is severely restricted rather than banned absolutely.
Polycyclic aromatic hydrocarbons (PAHs)
Polycyclic aromatic hydrocarbons are a large group of chemical compounds with a similar structure comprising two or more joined aromatic carbon rings. Different PAHs vary both in their chemical characteristics and in their environmental sources and they are found in the environment both as gases and associated with particulate material. They may be altered after absorption into the body into substances that are able to damage the genetic material in cells and initiate the development of cancer, although individual PAHs differ in their capacity to damage cells in this way.
The speciated PAH inventory was first compiled for the 1996 emissions inventory (see “Speciated PAH Inventory for the UK” Wenborn MJ 1999) and has allowed a more detailed understanding of the PAH emissions in the UK.
There have been several pollutant classifications relating to PAHs. Although there are a vast number of PAHs, the NAEI inventory focuses on sixteen. These 16 PAHs have been designated by the United States Environmental Protection Agency (USEPA) as compounds of interest under a suggested procedure for reporting test measurement results (USEPA 1988). The estimated emissions for individual compounds are given in Appendix 5 (for the appendices of this report see http://www.naei.org.uk/). A subset of this includes six of the PAHs identified by the International Agency for Research on Cancer (IARC) as probable or possible human carcinogens (IARC 1987). In addition, the Borneff 6 PAHs (another subset focussing on the health impacts of the PAHs) have been used in some EC emission inventory compilations. A further subset of PAHs are those to be used as indicators for the purposes of emissions inventories under the UN/ECE’s Persistent Organic Pollutants Protocol. These classifications are given in the following table.
Table 6.3 The USEPA 16 PAH Primary Pollutants, and other PAH Subsets.
|
|
Included in the NAEI |
USEPA Priority pollutants (16 PAH) |
IARC Probable or possible Human carcinogens (6 PAH) |
Borneff (6 PAH) |
UN/ECE POPs Protocol Indicators for purpose of emission inventories |
|
Naphthalene |
ü |
ü |
|
|
|
|
Acenapthene |
ü |
ü |
|
|
|
|
Acenapthylene |
ü |
ü |
|
|
|
|
Fluorene |
ü |
ü |
|
|
|
|
Anthracene |
ü |
ü |
|
|
|
|
Phenanthrene |
ü |
ü |
|
|
|
|
Fluoranthene |
ü |
ü |
|
ü |
|
|
Pyrene |
ü |
ü |
|
|
|
|
Benz[a]anthracene |
ü |
ü |
ü |
|
|
|
Chrysene |
ü |
ü |
|
|
|
|
Benzo[b]fluoranthene |
ü |
ü |
ü |
ü |
ü |
|
Benzo[k]fluoranthene |
ü |
ü |
ü |
ü |
ü |
|
Benzo[a]pyrene |
ü |
ü |
ü |
ü |
ü |
|
Dibenz[ah]anthracene |
ü |
ü |
ü |
|
|
|
Indeno[1,2,3-cd]pyrene |
ü |
ü |
ü |
ü |
ü |
|
Benzo[ghi]perylene |
ü |
ü |
|
ü |
|
The main environmental impact of PAHs relate to their health effects, focusing on their carcinogenic properties. The most potent carcinogens have been shown to be benzo[a]anthracene, benzo[a]pyrene and dibenz[ah]anthracene (APARG 1996). The semi‑volatile property of PAHs makes them highly mobile throughout the environment via deposition and re-volatilisation between air, soil and water bodies. It is possible that a proportion of PAHs released in the UK are deposited in the oceans and/or subject to long range transport making them a widespread environmental problem.
In 1999 the Expert Panel on Air Quality Standards (EPAQS) published a recommendation for an air quality standard for PAHs. This standard was based on the use of benzo[a]pyrene as an indicator of the overall carcinogenicity of the PAHs present in the atmosphere. In August 2002 PAHs were included in the Air Quality Strategy for England (see Section 4.1) through the introduction of an objective relating to concentrations in ambient air.
Emissions of benzo[a]pyrene (BaP) and the total of the 16 PAH’s are summarised in Table 6.4. Aluminium production and anode baking (carried out for the aluminium industry) was the largest source of PAH emissions in the UK up until 1996 (contributing nearly half of the total PAH emission). Emissions since then have declined and in 2000 these sources accounted for only 13% of the emissions. This is a consequence of investment in abatement equipment following from the authorisation regime implementing the Environmental Protection Act 1990. One of the anode baking plants has dramatically reduced its emissions and the other is timetabled to follow shortly.
Road transport combustion is currently the largest source of PAH emissions contributing 53% of the emissions in 2000. These figures have been substantially revised since the last NAEI Report. This is primarily a result of revisions to the emissions of napthalene from road transport combustion. Further detail on the methodology changes can be found in Appendix 1 (See http://www.naei.org.uk/). The next largest sources of emissions in 2000 were domestic combustion and non -ferrous metal production.
Emissions of PAH and BaP from domestic combustion increased between 1997 and 1999 but declined in 2000. This reflects the increased consumption of coal in the domestic sector during 1997 to 1999 and the subsequent decline in 2000.
There are several source sectors relevant to PAHs which have been targeted for improvement:
· Wood treatment may be a significant source of some of the lighter PAHs such as acenapthene, fluorene and anthracene. Currently this source is not included due to a lack of available data. However, data is being sought, and the feasibility of including emission estimates from this source will be determined.
· Emissions from bitumen production and use have not been estimated due to a lack of emission data. It is possible that bitumen use is a significant source of benzo[a]pyrene and other PAHs.
The BaP inventory has been updated to incorporate new information regarding emission factors and activity data on sources of BaP. The new estimates differ significantly from the last NAEI Report (Goodwin et al., 2000). Current total BaP emissions for 1999 are approximately 23% lower than those previously estimated for 1999.
The most notable changes to the BaP inventory are significantly reduced emissions from some industrial sources and smaller road transport emissions. Further detail can be found in Coleman et al., 2001.
Increased measurement of PAHs by both industry and regulators, particularly in the aluminium sector, has allowed improvements in the precision of the emission estimates. The uncertainties associated with the emissions estimates of PAHs are considered in Section 6.4.
Table 6.4
UK emissions of PAHs (Emissions of individual PAHs are given in Appendix 5- see
http://www.naei.org.uk/)
Table 6.4a
Emissions of 16 PAHs1 (tonnes)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
6 |
6 |
5 |
4 |
4 |
4 |
4 |
3 |
4 |
3 |
3 |
0% |
|
Petroleum Refining Plants |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
5 |
5 |
4 |
0% |
|
Other Comb. & Trans. |
10 |
10 |
7 |
4 |
2 |
1 |
1 |
1 |
1 |
1 |
1 |
0% |
|
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
765 |
786 |
760 |
739 |
591 |
464 |
485 |
471 |
488 |
523 |
411 |
18% |
|
Comm/Pub/Agri Comb. |
32 |
29 |
19 |
21 |
19 |
16 |
17 |
18 |
10 |
4 |
3 |
0% |
|
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
24 |
23 |
23 |
22 |
23 |
23 |
23 |
23 |
23 |
23 |
19 |
1% |
|
Other Ind. Comb. |
394 |
434 |
521 |
422 |
407 |
381 |
317 |
236 |
148 |
156 |
85 |
4% |
|
Production
Processes |
|
|
|
|
|
|
|
|
|
|
|
|
|
Non-Ferrous Metals |
3490 |
3354 |
3219 |
3083 |
2947 |
2307 |
735 |
432 |
394 |
277 |
276 |
12% |
|
Processes in Industry |
107 |
99 |
91 |
86 |
87 |
87 |
87 |
87 |
86 |
82 |
83 |
4% |
|
Solvent Use |
104 |
100 |
97 |
94 |
90 |
87 |
83 |
80 |
76 |
73 |
69 |
3% |
|
Road Transport |
|
|
|
|
|
|
|
|
|
|
|
|
|
Combustion |
2315 |
2274 |
2169 |
2110 |
2082 |
1900 |
1776 |
1627 |
1412 |
1294 |
1141 |
50% |
|
Other Trans/Mach |
9 |
9 |
9 |
9 |
8 |
6 |
6 |
5 |
4 |
4 |
4 |
0% |
|
Waste |
66 |
66 |
66 |
66 |
66 |
66 |
66 |
65 |
65 |
65 |
65 |
3% |
|
Agriculture |
933 |
800 |
582 |
12 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Nature (Natural
Fires) |
95 |
95 |
95 |
95 |
95 |
95 |
95 |
95 |
95 |
95 |
95 |
4% |
|
TOTAL |
8353 |
8090 |
7667 |
6770 |
6425 |
5441 |
3697 |
3146 |
2810 |
2604 |
2259 |
100% |
Table 6.4b Emissions of BaP2 (tonnes)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Petroleum Refining Plants |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Public Power (waste incin) |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Other Comb. & Trans. |
0.1 |
0.1 |
0.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
6.1 |
6.3 |
6.0 |
5.8 |
4.5 |
3.4 |
3.6 |
3.4 |
3.6 |
3.9 |
2.9 |
27% |
|
Comm/Pub/Agri Comb. |
0.3 |
0.2 |
0.2 |
0.2 |
0.2 |
0.1 |
0.1 |
0.2 |
0.1 |
0.0 |
0.0 |
0% |
|
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
0.1 |
0.1 |
0.0 |
0.0 |
0.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0.1 |
0.0 |
0% |
|
Other Ind. Comb. |
0.0 |
0.0 |
0.1 |
0.1 |
0.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Production
Processes |
|
|
|
|
|
|
|
|
|
|
|
|
|
Non-Ferrous Metals |
24.6 |
23.7 |
22.7 |
21.8 |
20.8 |
16.3 |
5.2 |
3.9 |
3.0 |
2.1 |
2.0 |
19% |
|
Processes in Industry |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.1 |
1% |
|
Solvent Use |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Road Transport |
|
|
|
|
|
|
|
|
|
|
|
|
|
Combustion |
5.3 |
4.6 |
3.9 |
3.2 |
2.7 |
2.1 |
1.7 |
1.3 |
1.0 |
0.8 |
0.7 |
6% |
|
Other Trans/Mach |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Waste |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
18% |
|
Agriculture |
28.3 |
24.3 |
17.7 |
0.4 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Nature |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
2.9 |
27% |
|
TOTAL |
70 |
65 |
56 |
37 |
33 |
27 |
16 |
14 |
13 |
12 |
11 |
100% |
1 The PAHs selected are listed above in Table 6.3
2 Benzo[a]pyrene
Figure 6.1 UK Emissions of 16 PAHs (tonnes)
Figure 6.2 UK Emissions of Benzo[a]Pyrene (tonnes)
Figure 6.3 Spatially Disaggregated UK Emissions of Benzo[a]pyrene
Dioxins and Furans (PCDD/F)
The term “dioxin” is used to refer to the polychlorinated dibenzo-p-dioxins (PCDD) and “furan” is used for polychlorinated dibenzofurans (PCDF). There are 210 PCDD/F compounds in total, which can be described as "congeners"- i.e. different compounds within a family or group having a similar structure. Of these 210 compounds the emissions of importance are those of the 17 PCDD/Fs (7 PCDDs and 10 PCDFs) as defined by the NATO/CCMS (Committee on the Challenges of Modern Society 1988) international toxic equivalent (I-TEQ) scheme. TEQ schemes weight the toxicity of the less toxic congeners as fractions of the toxicity of 2,3,7,8-TCDD, the most toxic congener.
The inventory presented here is in terms of the sum of the weighted emissions expressed as ‘I-TEQs’ which are widely used in UK and European legislation. However, more recently the World Health Organisation (WHO) has suggested a modification to the values used to calculate the toxic equivalents for some of the PCDDs and PCDFs. They have also suggested that there is value in using a similar approach for the PCBs which have dioxin-like toxicity and combining the PCDD/F and PCB TEQs together. The International and the WHO toxic equivalence factors (TEFs) for PCDD/Fs are shown in Table 6.5
Table 6.5 The International and the WHO Toxic Equivalence Factors for PCDD/Fs
(the differences are highlighted)
|
Dioxins |
International TEFs |
WHO TEFs |
|
2,3,7,8 tetraetrachlorodibenzo-p-dioxin |
1 |
1 |
|
1,2,3,7,8 pentachlorodibenzo-p-dioxin |
0.5 |
1 |
|
1,2,3,4,7,8 hexachlorodibenzo-p-dioxin |
0.1 |
0.1 |
|
1,2,3,6,7,8 hexachlorodibenzo-p-dioxin |
0.1 |
0.1 |
|
1,2,3,7,8,9 hexachlorodibenzo-p-dioxin |
0.1 |
0.1 |
|
1,2,3,4,6,7,8 heptachlorodibenzo-p-dioxin |
0.01 |
0.01 |
|
Octachlorodibenzo-p-dioxin |
0.001 |
0.0001 |
|
|
|
|
|
2,3,7,8 tetra4chlorodibenzofuran |
0.1 |
0.1 |
|
1,2,3,7,8 pentachlorodibenzofuran |
0.05 |
0.05 |
|
2,3,4,7,8 pentachlorodibenzofuran |
0.5 |
0.5 |
|
1,2,3,4,7,8 hexachlorodibenzofuran |
0.1 |
0.1 |
|
1,2,3,6,7,8 hexachlorodibenzofuran |
0.1 |
0.1 |
|
1,2,3,7,8,9 hexachlorodibenzofuran |
0.1 |
0.1 |
|
2,3,4,6,7,8 hexachlorodibenzofuran |
0.1 |
0.1 |
|
1,2,3,4,6,7,8 heptachlorodibenzofuran |
0.01 |
0.01 |
|
1,2,3,4,7,8,9 heptachlorodibenzofuran |
0.01 |
0.01 |
|
Octachlorodibenzofuran |
0.001 |
0.0001 |
1 NATO/CCMS (1988) 2 WHO (1998)
PCDD/Fs have been shown to possess a number of toxicological properties. The major concern is centred on their possible role in immunological and reproductive effects. The main sources of PCDD/Fs are thermal processes, but they can also be released to the environment from some chemical processes.
PCDD/Fs can arise from any thermal process where chlorine is present. For example, coal and other solid fuels contain trace amounts of chlorine compounds which can under certain combustion conditions result in PCDD/F formation. In addition PCDD/Fs can be present in the feed stock material, or chlorinated impurities may be introduced into the feed stock of some thermal processes. The amount of chlorine required for PCDD/F formation may be small and consequently many processes have the potential to emit these pollutants. PCDD/Fs can also be emitted from the chemical production and use of polychlorinated aromatic pesticides and herbicides, many of which are now controlled. However, some chlorinated organic chemicals such as the wood preservative pentachlorophenol are still used in the UK and these have the potential to be sources of PCDD/Fs e.g. from the combustion of treated wood.
Estimated PCDD/F emissions for 1990-2000 are summarised in Table 6.6 below.
Table 6.6 UK emissions of PCDD/Fs (grams TEQ/year)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
137 |
137 |
157 |
200 |
267 |
223 |
120 |
63 |
23 |
19 |
14 |
4% |
|
Petroleum Refining Plants |
12 |
13 |
13 |
14 |
14 |
14 |
14 |
14 |
14 |
12 |
9 |
3% |
|
Other Comb. & Trans. |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
74 |
75 |
73 |
74 |
71 |
67 |
68 |
66 |
66 |
67 |
65 |
18% |
|
Comm/Pub/Agri Comb. |
98 |
100 |
91 |
80 |
71 |
56 |
43 |
33 |
24 |
24 |
21 |
6% |
|
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
50 |
49 |
48 |
48 |
48 |
48 |
48 |
49 |
47 |
45 |
41 |
11% |
|
Non-Ferrous Metals |
22 |
19 |
17 |
19 |
18 |
18 |
19 |
18 |
17 |
18 |
14 |
4% |
|
Other Ind. Comb. |
63 |
65 |
67 |
64 |
69 |
65 |
63 |
59 |
54 |
56 |
47 |
13% |
|
Production
Processes |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel |
31 |
26 |
28 |
29 |
29 |
30 |
28 |
30 |
26 |
17 |
17 |
5% |
|
Non-Ferrous Metals |
6 |
6 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
6 |
2% |
|
Processes in Industry |
6 |
5 |
5 |
4 |
4 |
4 |
4 |
3 |
3 |
3 |
3 |
1% |
|
Solvent Use |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Road Transport |
|
|
|
|
|
|
|
|
|
|
|
|
|
Combustion |
29 |
26 |
23 |
20 |
18 |
16 |
14 |
11 |
8 |
6 |
5 |
1% |
|
Vehicle Fires |
6 |
6 |
6 |
6 |
6 |
7 |
7 |
7 |
7 |
7 |
7 |
2% |
|
Other Trans/Mach |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
0% |
|
Waste |
|
|
|
|
|
|
|
|
|
|
|
|
|
Landfill |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0% |
|
Waste Incineration |
586 |
580 |
561 |
517 |
370 |
307 |
195 |
99 |
103 |
104 |
104 |
29% |
|
Other Waste Treat. & Disp. |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Agriculture |
57 |
49 |
36 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Nature |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
2% |
|
TOTAL |
1184 |
1164 |
1138 |
1089 |
999 |
869 |
637 |
466 |
406 |
390 |
360 |
100% |
The largest sources of PCDD/F emission has bee, and still is, waste incineration. However emissions from waste incineration have fallen rapidly from 1993 to 2000. This significant trend has been driven by the introduction of control measures. MSW incinerators not meeting the new standards closed in the period leading up to December 1996. New designs of MSW incinerator result in significantly lower levels of PCDD/F emissions.
The relatively low emissions from chemical incinerators reflects the use of rotary kilns and the incorporation of a secondary combustion chamber in the process to destroy organic contaminants together with the relatively low waste throughput and advanced pollution abatement equipment. However, clinical waste incineration remains a significant source. This is due to the fact that emissions from clinical waste incinerators (although showing significant reductions) have not been reducing as rapidly as the total PCDD/F total.
Figure 6.4 UK Emissions of PCDD/Fs (grammes TEQ)
Emissions from power stations are fairly low because the combustion is efficient and the post‑combustion fly ash temperatures are rapidly reduced. The emission factors associated with industrial and domestic coal combustion are significantly higher and sum to give a similar contribution, even though the coal consumption is less. However, emissions from all three sectors have decreased with the reduction in the quantity of coal burned.
Emissions from open agricultural burning and accidental fires are included in the agricultural and nature sectors. The former has declined to near zero since the cessation of most agricultural burning. Accidental fires are currently treated as a source of constant magnitude, and consequently, the percentage contribution from this sector to the total PCDD/F emission has risen as emissions from other significant sectors have decreased.
There are significant emissions from sinter plants owing more to the large gas volumes emitted than to high concentrations. Emissions from iron and steel plants are probably underestimated since only electric arc furnaces are considered. Scrap used in electric arc furnaces and secondary non-ferrous metal production will contain chlorinated impurities such as plastics and cutting oil which contribute to PCDD/F formation.
It is generally accepted that the source of PCDD/F emissions
from road transport are the 1,2-dichloroethane scavengers added to leaded
petrol. Over recent years both the
consumption of leaded petrol, and the lead content of leaded petrol has
decreased. Consequently the emissions of PCDD/F from this sector have
decreased. Unleaded petrol and diesel is likely to contain only trace
quantities of chlorinated impurities. For 2000, the contribution to the PCDD/F
emission total from road transport was 1%.
Figure 6.5 Spatially Disaggregated UK Emissions of PCDD/F
Polychlorinated biphenyls (PCBs)
PCBs are synthetic organic compounds that have mainly been used in electrical equipment as dielectric insulating media.
PCBs have been linked with effects such as reduced male fertility and long-term behavioural and learning impairment- they are classified as probably carcinogenic to humans. Certain PCBs have been assessed as having dioxin-like effects. PCBs are extremely persistent in the environment and possess the ability to accumulate in the food chain. These compounds are highly insoluble in water but accumulate in body fat. Present human exposure is probably dominated by the accumulation through the food chain of the PCBs present in environmental reservoirs such as soils and sediments as a result of previous releases to the environment.
PCBs have not been manufactured and used in the UK for many years, but old PCB-containing equipment still exist. It is estimated that 81% of primary PCB emissions to the atmosphere are associated with such appliances. These emissions primarily arise from in-service appliances; however emissions during disposal are also considered to be significant. Large quantities of PCBs are thought to have been disposed of to landfill in the past, mainly in the form of electrical components or fragmentiser residues, but now such equipment containing PCBs are disposed of by chemical incineration. This process ensures significant reduction in the amount of PCBs being released into the environment. PCBs are also emitted from the soil having previously been deposited there from the air.
PCB speciation has been incorporated into the emission estimates since the 1998 inventory. A summary of the total PCB emission estimates for 1990 to 2000 is given below in Table 6.7 (detailed emission estimates and TEQs are give in Appendix 8, see http://www.naei.org.uk/).
Table 6.7 - Summary of PCB Emissions in the UK (kg)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
91 |
90 |
84 |
72 |
60 |
57 |
52 |
51 |
50 |
44 |
49 |
3% |
|
Other Comb. & Trans. |
4 |
1 |
4 |
4 |
4 |
4 |
3 |
4 |
4 |
4 |
4 |
0% |
|
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
23 |
25 |
22 |
24 |
20 |
15 |
15 |
16 |
16 |
16 |
10 |
1% |
|
Comm/Pub/Agri Comb. |
2 |
2 |
2 |
2 |
2 |
1 |
1 |
1 |
1 |
1 |
1 |
0% |
|
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
38 |
37 |
37 |
36 |
37 |
37 |
38 |
39 |
39 |
40 |
36 |
2% |
|
Other Ind. Comb. |
6231 |
5727 |
5223 |
4718 |
4215 |
3710 |
3205 |
2701 |
2196 |
1692 |
1187 |
70% |
|
Production
Processes |
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel |
491 |
419 |
438 |
458 |
428 |
394 |
373 |
387 |
400 |
243 |
249 |
15% |
|
Processes in Industry |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
Waste |
|
|
|
|
|
|
|
|
|
|
|
|
|
Landfill |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
0% |
|
Waste Incineration |
159 |
159 |
158 |
158 |
155 |
154 |
153 |
149 |
149 |
149 |
149 |
9% |
|
Other Waste Treat. & Disp. |
80 |
81 |
78 |
81 |
73 |
64 |
55 |
46 |
38 |
29 |
20 |
1% |
|
Agriculture |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
|
TOTAL |
7123 |
6544 |
6048 |
5554 |
4993 |
4439 |
3898 |
3395 |
2894 |
2217 |
1706 |
100% |
Figure 6.6 UK Emissions of PCBs (kg)
Sales of PCBs in the UK were stopped in 1986, though it is thought that they are still manufactured in some countries. The total PCB emission in 1990 was dominated by leaks from capacitors (87% of total emission), and this is the case for 2000 (70% contribution). However, not all electrical equipment containing PCBs is readily identifiable. Emissions from electrical equipment will probably continue, and will only start to fall significantly as the relevant electrical equipment is either destroyed or reaches the end of its working life.
In 1997 an Action Plan was published by DETR (now Defra) which laid out the commitments made by the UK at the Third International North Sea Conference at the Hague in 1991 in accordance with the requirements of Directive 96/59/EC. Regulations now require all PCB holders in the UK to report their stocks to the relevant regulatory bodies. These stocks (except for certain exemptions) were destroyed before the end of December 2000.
PCBs can be formed in trace amounts from chlorinated precursors in thermal processes such as scrap metal recycling. As a result, there are significant emissions from the iron and steel industrial sector, as with PCDD/Fs.
PCBs occur in sewage sludge due to their persistent nature, and may occur in significant quantities. Not all the PCBs spread on land will volatilise but the potential for emissions to air is greater than that of landfill. The emission estimate comprises only 1% of the total and is highly uncertain. Emissions arise from waste incineration and refuse derived fuel production result from the PCB content of the waste.
Pesticide Emissions
Although there is little available information to enable accurate estimates of pesticide emissions to air, the emission estimates presented here follow from significant improvements to the earlier emission estimates first made in 1996.
Despite these improvements, the confidence in the accuracy of these estimates is low. Relevant data is currently scarce with the majority of emission factors coming from the USA or Europe. The emission factors used here have been derived for a particular method of pesticide application (during specific atmospheric conditions), which may not be representative of the situation in the UK. Until further data becomes available it is difficult to reduce the uncertainty associated with these estimates. At present no relevant measurement programmes are known of, and therefore the possibility of acquiring additional data is considered to be poor.
Pesticide emissions to the air occur predominately through three pathways: during manufacture, during application and volatilisation after application. Tables 6.8, 6.9 and 6.10 show the estimated emissions of lindane (g-HCH), pentachlorophenol (PCP) and hexachlorobenzene (HCB) respectively.
Lindane (g HCH)
Acute (short-term) effects caused by the inhalation of lindane consist of irritation of the nose and throat, as well as effects on the blood. Chronic (long-term) effects through inhalation have been associated with effects on the liver, blood, immune and cardiovascular systems.
Lindane is applied as an insecticide and fungicide in agriculture and is used for wood preservation and in domestic and veterinary formulations. Until 1990 lindane was also used as a remedial wood treatment i.e. in a curative role rather than a preservative/preventative. However, data on quantities used for a remedial wood treatment prior to 1990 are not available.
HCH exists in several isomers, however as a result of regulation in the UK, g-HCH accounts for more than 99% of the total HCH use. Consequently only the g isomer has been considered in any detail here. The emission estimates presented in Table 6.8a were made assuming that emissions arise from: the application of g-HCH, treated wood and agricultural and domestic use. g-HCH emissions are dominated by emissions from treated wood and wood preserving sources, contributing 68% and 11% to the 2000 total emission respectively. Emissions from wood preserving are expected to fall.
Emissions from agricultural activities are also significant, accounting for around 21% of total 2000 g-HCH emissions. These emissions are based on statistics giving the use of pesticides containing lindane, obtained from the Pesticide Usage Survey Group (MAFF, 1991a,b,c; 1992a,b,c,d) The emission factors used are taken from van der Most et al (1989).
Emissions of g-HCH arising from domestic applications are thought to be comparatively small. However, usage statistics are scarce and were only available for 1988 ( DOE, 1989). Emission factors are taken from van der Most et al (1989).
Table 6.8a - Summary of g-HCH Emissions in the UK (tonnes).
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Solvent Use |
|
|
|
|
|
|
|
|
|
|
|
|
|
Treated Wood |
57 |
51 |
46 |
41 |
37 |
33 |
30 |
27 |
24 |
22 |
22 |
68% |
|
Wood Preserving |
36 |
28 |
21 |
17 |
13 |
10 |
8 |
6 |
5 |
5 |
4 |
11% |
|
Agriculture |
|
|
|
|
|
|
|
|
|
|
|
|
|
Domestic Pesticide Use |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
2% |
|
Agriculture Pesticide |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
19% |
|
TOTAL |
99 |
85 |
74 |
65 |
57 |
50 |
45 |
40 |
36 |
33 |
32 |
100% |
Figure 6.7 UK Emissions of g-HCH (tonnes)
For completeness, the total emissions of HCH are also included here (see Table 6.8b below), although the differences are obscured due to rounding. These total HCH emissions estimates assume the worst case scenario of 1% contribution from non g isomers to the HCH total.
Table 6.8b - Summary of Total HCH Emissions in the UK (tonnes)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Solvent Use |
|
|
|
|
|
|
|
|
|
|
|
|
|
Treated Wood |
57 |
52 |
46 |
42 |
38 |
34 |
30 |
27 |
25 |
22 |
22 |
68% |
|
Wood Preserving |
36 |
28 |
22 |
17 |
13 |
10 |
8 |
6 |
5 |
5 |
4 |
11% |
|
Agriculture |
|
|
|
|
|
|
|
|
|
|
|
|
|
Domestic Pesticide Use |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
2% |
|
Agriculture Pesticide |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
19% |
|
TOTAL |
100 |
86 |
75 |
65 |
57 |
51 |
45 |
40 |
36 |
34 |
33 |
100% |
Pentachlorophenol (PCP)
Pentachlorophenol is associated with both acute and chronic effects on humans through inhalation. Acute effects can lead to eye irritation as well as having liver, blood and neurological effects. Long-term (chronic) exposure can result in effects on the respiratory tract, immune system, liver, kidneys, blood as well as the eyes and nose.
Pentachlorophenol is used as a biocide, and is effective in destroying insect eggs. It is used in the timber and textile industries. The emission estimates given here also include emissions of sodium pentachlorophenoxide (NaPCP) and pentachlorophenyl laureate (PCPL) as well as PCP since these are also included in the proprietary formulations.
The estimated PCP emissions for 1990 to 2000 are given in Table 6.9. The largest percentage contribution to the total PCP emission arises from wood that has been treated within the last 15 years. This accounts for some 89% of the 2000 total PCP emission.
Once again it is very difficult to be certain of these estimates due to the lack of research into emission rates and limited knowledge of quantities used both in the year of the estimate and in previous years. An emission factor of 3% of the wood content per year was used- the same method used for lindane.
PCP emissions from the textile
industry primarily arise from volatilisation during application as a cotton
preservative. Emission factors used
were based on a study of PCP emissions in the UK (Wild, 1992) who report that
approximately 30% of the applied PCP is lost through volatilisation. Emissions from this sector are comparatively
small.
PCP is used in the agricultural sector as the active ingredient in disinfecting wooden trays used in mushroom farming (classified as solvent use). Usage statistics are reliable coming from the Pesticide Usage Survey Group (MAFF, 1991a,b,c; 1992a,b,c,d). The emission factor assumes 30% loss due to volatilisation (Wild, 1992). Emissions from this sector are comparatively small.
Table 6.9 - Summary of PCP Emissions in the UK (tonnes)
|
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
|
BY UN/ECE CATEGORY |
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
0.1 |
0.1 |
0.1 |
0.1 |
0.2 |
0.2 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0% |
|
Comb. in
Comm/Inst/Res |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Combustion in Industry |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Production
Processes |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
Solvent Use |
|
|
|
|
|
|
|
|
|
|
|
|
|
Textile Coating |
3.0 |
3.0 |
3.0 |
3.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
NaPCP Treated Wood |
3.6 |
3.6 |
3.6 |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
0% |
|
PCP Treated Wood in Use |
474.5 |
474.5 |
474.5 |
474.5 |
466.6 |
458.9 |
451.5 |
444.3 |
437.3 |
430.6 |
424.1 |
89% |
|
PCP Treated Wood |
6.2 |
6.2 |
6.2 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0% |
|
PCP in Imported Wood |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
50.0 |
11% |
|
Road Transport |
0.0 |
0.0 |
0.0 |
0.0 |