ly connect with real world activities. For each challenge, we arrange individual risks into hazard -pathway -receptor combinations and semi -quan titativ ely assign risk scores to indicate and rank the rel ative harm of various activiti es within the sector. As a matter control, we specifical ly exclude the M anagement of CDW from disasters, war and conflict are kept of scope here, as specific sub -cases warrant a specialist review; these are as shown outside the system boundary (Figure 1). Figure 1: Material flow system for construction and demolition waste (CDW). C&D Waste generation C&D waste treatment facility Wetland Infills Natural disaster System boundary Disposal Uncollected Collected Diffuse dumps Dumpsites Landfill Transport Recycling (formal) Collection for recycling (informal) Transport of losses Demolition from war/ conflict Aquatic environment Construction (buildings, roads, bridges, etc.) Demolition for urbanisation Recycled concrete aggregates Recycled bricks/ ceramics Scrap metal/Steel Gravel Wood Open burning Incineration 8 2. Methods 2.1. Systematic review PRISMA guidelines (Moher et al., 2009) were adapted according to a method reported by Cook et al. (2020) to carry out a systematic review to explore the following research questi ons (RQ):  RQ1: What evidence exists to indicate risk to public and occupational safety posed by CDW?  RQ2: What are the comparative risks to public and occupational safety that arise from the management of CDW ?  RQ3: What research could be carried out that would have the greatest impact on harm reduction in the CDW management sector ? One at a time sensitivity analysis was used to optimise Boolean search terms (listed in Section S.1.1 ) to retrieve literature from Scopus, We b of Science and Google Scholar. Sources were included and excluded according to the criteria in Table S1 (Section S.1.2 ). Snowball and citation searching (Cooper et al., 2018) was used to obtain further relevant information that had not been revealed during the systematic search. Several further relevant sources were se arched in more detail, such as The World Bank (2020) , International Labour Organization (2020c) , World Health Organization (2020) , Health and Safety Executive (2020b) (HSE). Combination s of hazards, pathways and receptors were identified from the literature and arranged on the basis of realistically e xperienced scenarios as described by Cook et al. (2020) ; enabling the preparation of source -pathway -receptor flow diagrams as illustrated in Figure 2. 9 Figure 2: Summary of the main sources, pathways and receptors for hazar ds associated with construction and demolition waste (CDW). Gravity Dust Atmosphere Inhalation Adult citizens Occupational (formal) Soil Groundwater Rivers streams & lakes Surface water Sediments Demolition activity Deposition Kinetic energy in mechanical equipment Construction waste handling Physical injury Comminution/ abrasion Mouthing Child citizens Ingestion Uptake in cro ps Food Building materials Products of incomplete combustion Substances present in building materials Substances from previous use of building Co-disposed materials Released during combustion Released during thermal deconstruction Ash Bio-degradation Gas production Inhalation Migration to the surface of material (thermodynamic equilibrium ) Attenuation Leaching Occupational (informal) Drinking water Ingestion Sources Pathways Receptors Receptor Route of human exposure Environmental compartment Substance or material Transfer process Legend 10 2.2. Risk based approach Each hazard -pathway -receptor combination was indicatively assigned a risk score based on the likelihood of it occurring and potential severity to different receptors ( Table 1 and Table 2) based on an approach described by Cook et al. (2020) , that was adapted from World Health Organization (2012) , Hunter et al. (2003) , Kaya et al. (2018) and Burns et al. (2 019). The reader should note that this process was not intended to quantitatively assess risk, but to indicate and rank the relative risks to prioritise future research agenda; the combined and ranked results are shown in Table S 4 (Section S.4 ). Table 1: Matrix used to calculate the relative risk of each hazard -pathway -receptor scenario. Consequence Very slight Slight Moderate Severe Very severe 1 2 3 4 5 Likelihood Very unlikely 1 1 2 3 4 5 Unlikely 2 2 4 6 8 10 Likely 3 3 6 9 12 15 Very likely 4 4 8 12 16 20 Inevitable 5 5 10 15 20 25 Table 2: Colour coding used to rank hazard potential qualitatively in each category. Red (R) High harm potential Amber (A) Medium/high harm potential Yellow (Y) Medium/low harm potential Green (G) Low harm potential Grey Insufficient data 3. Challenge 1: Handling and physical processing of construction and demolition waste (CDW) 3.1. Context The hazard -pathway -receptor ( H-P-R) linkage s necessary for potential hazards to be actualised on construction and demolition sites as a consequence of handling and physical processing are shown in Figure 3. Broadly these are delineated here by : hazards that exist from materials or s ubstances in construction waste or the previous use of buildings, and physical accidents that take place during deconstruction (demolition) and /or wa ste removal activities. 11 Figure 3: Hazard exposure conceptual model ( hazard –pathw ay–receptor) associated with the handling and physical processing of construction and demolition waste (CDW). 3.2. Accidents involving CDW Occupational accident data are available from a variety of sources worldwide including from national government institutio ns, supra -national sources such as the European Union (EU) and from international non-governmental organisations ( NGOs ) such as the International Labour Organization. According to data from 2016, 20% of all workplace fatalities occurred in the construction and demolition sector (International Labour Organization, 2020a) , a category that is rarely reported as two separate components. This is more than twice the proportion of workers participating in this economic activity according to (Mella and Savage, 2018) , who sugges t it that 8.6% of the global workforce are engaged in construction. Non-fatal accidents are lower than the fatalities as a proportion of the workforce representing 10% of reported non -fatal injuries, (International Labour Organization, 2020b) , but still disproportionately higher. Gravity Sources Migration and aerosolisation Dust Atmosphere Inhalation Adult citizens Occupational (formal) Pathway s Receptors Soil Groundwater Rivers streams and lake s Surface water Sediments Receptor Route of human exposure Environmental compartment Substance or material Transfer process Legend Demolition activity Deposition Substances present in building materials Substances from previous use of build ing Kinetic energy in mechanical equipment Construction waste handling Physical injury Building materials Comminution/a brasion Mouthing Child citizens Ingestion Uptake in crops Food 12 Specific data related to waste and CDW are uncommon. Eurostat (2020) publishes accident statistics reported by European Union member sta tes under their obligations to abide by Regulation 1338/2008 (European Union, 2008b) . Data are reported by businesses and institutions to their relevant national governments and then published on Eurostat by NACE (economic) activity. Only accidents requiring more than three days absence from work and fatalities are reported (hereafter ‘>3 day accidents’); therefore, accidents or near misses that do not result in significant injury are not included in the statistics (European Commission, 2009) . Furthermore, Eurostat highlights that many accidents may not be captured because of the data collection method (Eurostat, 2019) . For example, if health insurance companies are the source of data collection (as is the case for several member states), then th e uninsured may be not be included. There are also several other potentially underrepresented parties, such as self -employed workers who may not report accidents; and public sector, mining and fishing workers who may be covered under specific insurance sch emes that do not necessarily submit data (European Commission, 2009) . Some member states provide more granular (‘Phase III’) information on the ‘mode of injury’, ‘deviation’, a nd ‘material agent’ involved in accidents reported (Eurostat, 2010) . However, these categories are not reported comprehensively as the member states are not obliged to do so. In practice, some member states report under every category, some one or two, and others none at all (European Commission, 2009) . One of the Phase III accident categories reported is ‘bulk waste’. Queried together with the NACE category for ‘construction and demolition’, >3 day accidents inv olving bulk waste per 100,000 people are shown in Figure 4 and Figure 5. In all cases, the rate has changed little over the four year period, with approximately 3,000 >3 day accidents per 100,000 people reported in the construction and demolition sector, of which approximately fi ve are related to bulky waste. 13 Figure 4: Rate of accidents in the EU28 resulting in more than three days absence from w ork; NACE activity: construction; after Eurostat (2020) . Figure 5: Rate of accidents in the EU28 resulting in more than three days absence from work; NACE activity: construction; material agent: bulk wast e; after Eurostat (2020) . In Figure 6 and Figure 7, the annual fatality rates for construction and demolition and bulky waste are shown respective ly, with apparently little change in the four year period in each category. Figure 6: Rate of accidents in the EU28 resulting in a fatality within one year; NACE activity: construction; after Eurosta t (2020) . Figure 7: Rate of accidents in the EU28 resulting in a fatality within one year; NACE activity: construction; material agent: bulk waste; after Eurostat (2020) . While the Eurostat data shown in Figure 5 and Figure 7 provide s an indication of occupational accidents that have been recorded as involving ‘bulk waste’, it is suggested 2,920 2,8523,010 2,876 05001,0001,5002,0002,5003,0003,500 2014 2015 2016 2017Accidents per 100,000 workers5.52 4.46 4.71 4.73 0.001.002.003.004.005.006.00 2014 2015 2016 2017Accidents per 100,000 workers 6.14 6.245.80 5.60 0.01.02.03.04.05.06.07.0 2014 2015 2016 2017Accidents per 100,000 workers0.02 0.02 0.0000.0050.0100.0150.0200.025 2014 2015 2016 2017Accidents per 100,000 workers 14 here, that several types of acci dent involving waste are likely to be omitted f rom this category and included in others. For instance, exposure to asbestos waste and demolition are grouped under the title ‘construction’ rather than being reported under distinct sub -categories. 3.3. Accidents during the demolition phase Demolition work is often expected to be faster and less costly than construction work and hence, sometimes results in shortcuts being taken at the expense of occupational health and safety (Ertaş and Erdoğan, 2017) . Nonetheless, this section reveals that there is little specific data to evidence the risk of accidents resulting from demolition; a premise supported by at least two other authors (Ertaş and Erdoğan, 2017; Takahashi, 2019; Zaharuddin et al., 2009) . Hence, the level of risk exposure to accidents from this important waste activity is poorly understood. Three sources of information indicate the number of injuries and fatalities from demolit ion activities as a proportion of all activities ( Table 3). The data from the European Commission (European Commission, 2009) , originate from an older Eurostat dataset than Eurostat (2020) and report a specific Phase III sub -category of ‘Demolition’ for the EU15 in 2005. As discussed, there are significant inconsistencies in reporting of the Phase III categories a s well as several other factors that result in under -reporting. Furthermore, the dataset is more than 15 years old at the time of writing. However, given the paucity of data on this subject, and the representative size of the European Commission dataset, ( population of EU15 was 384.2 million in 2004 (European Commission, 2006) ), it provides the most substanti al coverage of demolition accident data revealed in this research. Table 3: Injuries and fatalities from demolition activities as a proportion of injuries and fatalities from all sectors. Ref Geog. Secondary source / data type n Time-frame Proportion of all fatalities Proportion of all injuries Proportion of all injuries & fatalities Maeda et al. (2003) JPN, Osaka City forensic post - mortem data Fatalities 67 1996 -2001 7.5% European Commission (2009) EUR ESAW Fatalities 2,307 2003 -2005 a 0.71% 0.16% 0.16% Injuries 1,709,648 2005 Total 1,711,955 Zaharuddin et al. (2009) AUS ASCC Total 14,869 2002 -2004 0.4% a Sample originally reported over 3 years, therefore divided by three in this ta ble. A bbreviations: Australian Safety & Compensation Council (ASCC); European Statistics on Accidents at Wor k (ESAW); number of samples (n); geographical context (Geog.). 15 As a proportion of injuries from all sectors, the European Commission (2009) data indicate s that 0.16% of all >3 day injuries and workplace fatalities combined occur in the demolition sector compared to 0.4% in Australia, as reported by Zaharuddin et al. (2009) (Table 3). In the EU15, the demolition sector reports a higher proportion (0.71%) of fatalities in comparison to the >3 day injuries. The only other data point that evidences fatalities in the demolition sector is the research by Maeda et al. (2003) who observed a consid erably higher proportion of fatalities from demolition activities from a single city in Japan between 1996 and 2001 in comparison to the European Commission. The Maeda et al. (2003) data are alarmingly high in the context of the European Commission rate, which is ap proximately 10 times lower. There is insufficient evidence from the two studies to explain this large disparity. However, there may be a variety of factors specific to the local conditions in Japan, such as corporate attitudes toward safety; differing regu latory framework; or possibly the influence of a single company’s record. Although the Maeda et al. (2003) dataset is small in comparison to the European Commission dataset, in other studies (Evans, 2014) data on fatalities have been reported to be more reliable than accident data, because almost all fatal injuries are reported to someone, unlike accidents which may not be. In any case, suc h a high comparative fatality rate warrants further investigation in Japan and other parts of the world to understand the proportion of demolition sector injuries and fatalities that exist elsewhere. Accident data for the demolition sector as a proportio n of construction and demolition as a whole are more numerous than data reported as a proportion of all accidents, with five sources identified ( Table 4). As the denominator (construction and demolition) is a smalle r dataset, it is unsurprising that the proportion of accidents is higher than for demolition activities as a proportion of all categories (reported in Table 3). 16 Table 4: Injuries and fatalit ies from demolition activities as a proportion of injuries and fatalities from construction and demolition combined. Ref Geog. Secondary source/data type n Time -frame Fatalities Non-fatal injuries Total Number Proportion of all fatalities Number Proportion of all injuries Number Proportion of all injuries and fatalities Gürcanli and Müngen (2013) TUR Eye-witness accounts from court records Fatalities 788 1972 -2008 30 3.8% 14 3.9% 44 3.8% Injuries 361 Total 1,149 Ertaş and Erdoğan (2017) AUS Australian Institute of Health and Welfare Total 8,300 2006 -2009 83 1% GBR British Market Research Bureau Total 5,813 nd 186 3.2% Zaharuddin et al. (2009) GBR Health and Safety Executive (HSE) Total 659 1997 -2005 47 7.13% European Commission (2009) EUR Eurostat – ESAW Fatalities 1,464 2003 -2005 a 16 1.09% 2,786 1.23% 2,802 1.23% Injuries 226,835 2005 Total 227,323 Takahashi (2019) JPN n/a Fatalities 1,646 2010 -2014 107 6.5% a Sample originally reported over three years, therefore divided by three in this table. Abbre viations: number of samples (n); geographical context (Geog.); European Statist ics on Accidents at Work (ESAW). 17 Whereas the proportio ns of fatalities and >3 day injuries by t he European Commission (2009) in Table 4 are broadly proportional to those reporte d in Table 3, the overall proportion of accident s and fatalities from demolition reported by Zaharuddin et al. (2009) are nearly six times higher. The Zaharuddin et al. dataset is smaller, and from an earlier timeframe, and the UK has greatly improved its health and safety r ecord for the construction and demolition sector since, as evidenced from the later and larger UK dataset reported by Ertaş an d Erdoğan (2017) , indicating the accident rate has halved. The data reported by Takahashi (2019) of demolition fatalities over a five year period in Japan ( Table 4), have some similarity with the data reported by Maeda et a l. (2003) for Osaka, Japan ( Table 3), in that the fatality rate of the sector is approximately six times higher than the European Commission and nearly twice the proportion reported by Gürcanli and Müngen (2013) in their study of Turkish eye -witness court tes timonies. Takahashi et al. noted that it was common practice among demolition workers in Japan to cut a hole in the floor of a building under deconstruction to pass valuable scrap metals through for recycling and that the technique for demolishing walls wa s to manually weaken the bottom before mechanically pushing walls over with a mechanical plant. While limited evidence was revealed to indicate the underlying causality of accidents, the testimony by Takahashi et al. ought to provide the basis for further investigation of attitudes toward safety in specific cultures. Japan is a HIC, and intuitively ought to possess the resources necessary to train and equip its workforce to carry out potentially hazardous activities under a safe system of work. Speculativel y, if conditions are as hazardous as the Japan data suggest s, then it is conceivable that many LIMICs with less rigid regulatory frameworks and less ingrained health and safety culture may also have a poor accident and fatality record. Understanding the ty pes of activity that result in injuries or fatalities and the type of accident itself is crucial to developing safe systems of work to mitigate the probability of them occurring in the future. In studies from both the USA (Ertaş and Erdoğan, 2017) and Japan (Takahashi, 2019) , demolition workers were most likely to suffer a fatality as a result of a fall from height or a building collapse ( Table 5). Zaharuddin et al. (2009) reported a similar proportion for demolition workers in the UK, with approximately 53% of fatal and non -fatal accidents being caused by collapse and 28% caused by a fall. While the data for these four accident types show s some congruence, other accident types reported in Table 5 are less consiste nt, making the data challenging to compare. 18 Table 5: Injuries and fatalities from specific activities or causes as a proportion of injuries and fatalities from demolition activit ies. Ref Geog. Secondary source/data type Receptor/ activity Time - frame Fatalities Non-fatal injuries Total Number Proportion of all fatalities Number Proportion of all injuries Number Proportion of all injuries and fatalities Ertaş and Erdoğan (2017) USA OSHA Collapse of building 1984 -2012 119 31.07% 69 25.56% 188 28.79% Fall from height 105 27.42% 66 24.44% 171 26.19% Struck by falling object/flying debris 73 19.06% 57 21.11% 130 19.91% Machinery 42 10.97% 14 5.19% 56 8.58% Slip/trip/fall 14 3.66% 25 9.26% 39 5.97% Electric shock 16 4.18% 2 0.74% 18 2.76% Fire 3 0.78% 13 4.81% 16 2.45% Ballistic injury a 2 0.52% 11 4.07% 13 1.99% Traffic accident 1 0.26% 1 0.37% 2 0.31% Asbestos ex posure 0 0.00% 3 1.11% 3 0.46% Other 8 2.09% 9 3.33% 17 2.60% Total demolition 383 100.00% 270 100.00% 653 100.00% Zaharuddin et al. (2009) GBR HSE (2008) Falls 1997 -2005 13 27.66% Transport 5 10.64% Collapse 25 53.19% Struck -by 2 4.26% Miscellaneous 2 4.26% Total demolition 47 100.00% Takahashi (2019) JPN Japan (Ministry of Health, Labour and Welfare 2018) Fall 2010 -2014 56 52% Collapse 20 19% Come flying (Flying object) b 9 8% Take crash (Crash) b 7 7% Get between ( Crush) b 6 6% Other 9 8% Total demolition 107 100% a Cuts/ scratches/ jamming/ hitting/ puncturing/ manual handling; b direct descriptions are shown and assumed translations are suggested in brackets. Abbre viations: number of samples (n) ; health and safety executive (HSE); Occupational Safety and Health Administration (OSHA) . 19 Analysis by Gürcanli and Müngen (2013) of eye -witness accounts of accidents over 36 years in the Turkish construction sector provide s some indication of the types of demolition activity that resulted in injuries and fatalities over the period ( Table 6). Compared to other reports, the injury and fatality data appear low in absolute number terms, with less than one fatality and slightly more than one injury over the 36 year period, compared to Japan which reports approximately 21 fatalities per year between 2010 and 2014 (Takahashi, 2019) (Table 5). Gürcanli and Müngen (2013) report an additional reason to query the low reported fatality and injury rates: the country has no specific health and safety legislation, suggesting that the lack of regulatory framework would result in an accident rate that far exceeded other countries where a framework exists. Table 6: Demolition work activity being carried out at the time of a ccident; after Gürcanli and Müngen (2013) . Receptor/activity Fatalities Non-fatal injuries Total fat and non -fatal Number Proportion of all fatalities Number Proportion of all injuries Number Proportion of all injuries and fatalities Demolition roof and slab 3 10.00% 2 14.29% 5 11.36% Demolit ion walls 16 53.33% 8 57.14% 24 54.55% Demolition structural elements a 9 30.00% 4 28.57% 13 29.55% Other demolition 2 6.67% 0 0.00% 2 4.55% Total demolition 30 100.00% 14 100.00% 44 100.00% a For example, columns and beam; Data sourced from eye -witness accounts from court records in Turkey between 1972 and 2008. Data reported by Gürcanli and Müngen (2013) only included cases that were examined by the courts, and the authors cautioned that, at the time of writing, official Turkish statistics are unreliable indicators of accidents because they on ly report injuries and fatalities for which a conviction was successful. If there is a societal aspiration to reduce accidents across the demolition sector, then the data shown in this section highlight the need for a more harmonised global system of repor ting, without which cost -effective interventions cannot be targeted where most needed. 3.4. Asbestos Asbestos is the generalised term used to describe a group of naturally occurring fibrous silicate minerals that have been used in a variety of commercial and industrial applications for many thousands of years (Furuya et al., 2018a) . Materially , asbestos has impressive physical properties such as insulation, tensile strength, and low density/strength ratio (lightness) (Dodson and Hammar, 2012) . Despite these attributes, asbestos is best known for 20 its carcinogenicity, linked to many thousands of deaths each year worldwide. There are six main types of asbestos ( Table 7), three of which have been sold commercially since the first large scale industrial extraction in Quebec in 1876 when approximately 50 tonnes was mined (Henderson and Leigh, 2012) . Table 7: Types of asbestos and their formulae; adapted from Henderson and Leigh (2012) . Common group Group type Asbestos type Chemical formula White asbestos Serpentine Chrysotile Mg 3Si2O5(OH) 4 Blue asbestos Amphiboles: commercial Crocidolite Na2(Fe 32+)(Fe 23+)Si 8O22(OH) 2 Brown asbestos Amosite (Fe, Mg) 7Si8O22(OH) 2 Fe>5 Never sold commercially but often found as contaminants in other asbestos products Amphiboles: non -commercial Tremolite Ca2Mg 5Si8O22(OH) 2 Anthophyllite (Mg, Fe) 7Si8O22(OH) 2Mg>6 Actinolite Ca2(Mg, Fe )5Si8O22(OH) 2 During the 20th century, asbestos became an increasingly popular material and was used in approximately 3,000 to 4,000 product applications, including insulation materials, cement reinforcement, roofing, brakes, fire resistant textiles, gas masks and wine filters (Frank, 2006; Henderson and Leigh, 2012; Ogunseitan, 2015) . Production rose sharply following the Second World War, reaching its peak in 1980 ( Figure 8), after which concerns over its safety resulted in successive bans across Europe and in the US (Kazan -Allen, 2019a) . Figure 8: Glo bal asbestos prod uction 1900 -2017; data from Virta (2006) and National Minerals Inf ormation Center (2018) . Abbreviations: metric tonnes (t) . Both Amphiboles (Crocidolite and Amosite) were effectively banned by the mid -1980s in most western countries and chrysotile asbestos has been banned in many countries since. Nonetheless, asbestos w as still consumed in 39 countries worldwide in 2017 ( Figure 9) and 01,000,0002,000,0003,000,0004,000,0005,000,000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2017Mass production (t) 21 production continued in four, with Russia producing nearly two thirds of the 1.1 Mt consumed worldwide that year ( Figure 10). Figure 9: Asbestos consumption by country in 2017 (t onnes ); data after National Minerals Information Center (2018) . Figure 10: Asbestos production by country in 2017 (t onnes ); data after National Minerals Information Center (2018) . According to Flanagan (2020) , reliable data on global asbestos production and consumption have not been published in recent years . There is also an apparent continuing downward trend in production, including the closure of the last mine extracting asbestos in Brazil in 2020 that accounted for 12% of global production in 2017 ( Figure 10). India and China are the largest asbestos consuming countries, representing nearly half of global consumption . Although the data since 2010 indicate s a general reduction in consumption in Russia and China, continued use is apparent in India ( Figure 11), where there are no restrictions on its production and consumption (Jadhav and Gawde, 2019) . Specific data are not available, but it has been reported that in India almost all asbestos is used in cement bonded sheet material (Burki, 2010) , and the International Chrysotile Association (nd) reports a similar picture elsewhere. Of course other applications continue, including: insulating protective equipment for fire - fighting and brakes for automobiles (Frank, 2006; Henderson and Leigh, 2012; Ogunseitan, 2015) . India 318,000 China 235,000 Russia 118,000Indonesia 105,000Uzbekistan 97,000Other 56,500Vietnam 43,100Thailand 42,600Brazil 40,300Sri Lanka 35,700Bangladesh 18,300Ukraine 16,000Kazakhstan 10,500 China 124,723 Russia 710,248Brazil 135,000Kazakhstan 192,700 22 Figure 11: Asbestos consumption trends for the top three consuming countries; data after National Minerals Information Center (2020) . Undisturbed, most forms of asbestos pose little danger to those in close proximity, particularly when the fibres have been encapsulated in resin ( for example, floor tiles) or cement ( for example roofing sheets) (Siegel, 1991) . Asbestos fibres are mineral and do not volatilise, so they only represent a hazard when they have been weathered or otherwise abraded from the m aterial after which solid particles can easily aerosolise (become suspended in the atmosphere) and be potentially inhaled (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, 2 012). In the lungs, the barbed asbestos particles become lodged, causing inflammation and scarring over time, and resulting in several diseases. The link between mesothelioma, a malignant cancer of the pleura, and both occupational and non - occupational ex posure to asbestos was established in the 1960s (Henderson and Leigh, 2012) and since then, occupational asbestos exposure has been the subject of more than 100 cohort studies and several reviews (Concha -Barrientos et al., 2004) ; the World Health Organization (WHO ) estimates that approximately 125 million living people have been exposed (Spasiano and Pirozzi, 2017) . Estimates of the n umber of deaths caused by asbestos exposure vary. Although it is linked to several diseases , including lung cancer, ovarian cancer and kidney cancer (Frank and Joshi, 2014) , the death rate for mesothelioma is a strong indicator as virtually all are thought to be a result of asbestos exposure (Driscoll et al., 2005; Stayner et al., 2013) . The WHO Mortality Database (World Health Organization, 2019) provides a record of reported cases of 0100,000200,000300,000400,000500,000600,000700,000 2010 2011 2012 2013 2014 2015 2016 2017Consumption (t yr-1)China India Russia 23 mesothelioma from countries that submit data. Vanya et al. (2011) analysed the database entries from 1994 to 2008, finding generally low levels of reporting. For instance, in 1995 just four countries submitted data, rising to 75 in 2003 and 100 by 2007. As shown in Table 8, cases were almost three times higher between 2001 and 2 008 compared to 1994 to 2000. Almost 88% of cases reported were in high income countries, with negligible numbers reported in low income countries. This is partly explained by the number of countries that submitted data; clearly much greater in the HICs. H owever, mesothelioma is still a comparatively rare condition that is not always easy to diagnose; often requiring cumulative experience which can take many years for the medical profession to accumulate (Odgerel et al., 2017) . Therefore it is likely that many cases in LIMICs are not classified as mesothelioma and are consequently not reported, rather than the low numbers of cases being a reflection of safe working practices around asbestos (Li et al., 2014) . Table 8: Deaths from mesothelioma reported to the World Health Organization (2019) , as analysed by Vanya et al. (2011) . Geog. n Temporal scope Deaths All Male Female Global 63 1994 -2000 22,305 77 2001 -2008 69,984 83 1994 -2008 92,253 72,000 20,252 High income 39 1994 -2008 81,313 Middle income 37 10,906 Low income 2 22 Not available 5 12 Abbreviations: number of samples (n). Taking a mean of t he global deaths reported between 2001 and 2008 ( Table 8), indicates 8,748 annual cases of mesothelioma each year, considerably lower than a previous estimate of 43,000 per annum estimated in 2005 by Driscoll et al. (2005) . To estimate the unreported cases, Odgerel et al. (2017) used the WHO Mortality Database (World Health Organization, 2019) to model deaths from mesothelioma in the coun tries that either didn’t report or appeared to underreport. The study based the estimates on the historical use of asbestos in each country, the level of employment in the construction sector, and the continental average. 24 For example, in Figure 12, the continental adjusted data are compared with the reported data, revealing huge underreporting in Asia and Africa. Figure 12: Global mesothelioma deaths region reported to the World H ealth Organization (2019) alongside adjusted data calculated by Odgerel et al. (2017) . As with the reported data, the proportion of women dying from mesothelioma in the estimated (adjusted) data were approximatel y 23%, a likely reflection of the number of men working in construction compared to women worldwide. When stratified by the World Bank income category (The World Bank, nd), the differences between the reported deaths and modelled deaths are stark ( Figure 13), with virtually all reporting taking place in HICs and almost none in lower middle income countries (LMCs ) or low income c ountries (LICs). 2053,559 1,89315,776 3,5864,7338,63011,424 697 766 02,0004,0006,0008,00010,00012,00014,00016,00018,000 Reported (1)Adjusted (60)Reported (10,9)Adjusted (46)Reported (14)Adjusted (52)Reported (32)Adjusted (53)Reported (2)Adjusted (17) Africa Asia Americas Europe OceaniaFatalities per annum Women Men 25 Figure 13: Global mesothelioma deaths by income category reported to the World Health Organization (2019) alongside adjusted data calculated by (Odgerel et al. , 2017) . Income categories were assigned to the estimated data according to each county’s categorisation in the last year of the three year averaged estimates reported by Odgerel et al. Abbreviations : high-income country (HIC); upper -middle -income country (UMC); lower -middle -income country (LMC ); low -income country (LIC). Odgerel et al. (2017) proffered their ‘asbestos use’ adjustment as the most reliable estimate of the three adjustments; with an annual average d eath rate of 38,400, it was fairly close to the 43,000 estimated by Driscoll et al. (2005) a decade earlier. However, although mesothelioma deaths are a reliable indicator, they are only one of several diseases tha t are attributable to asbestos exposure. Various estimates have been suggested for the total number of deaths from all asbestos related diseases, ranging from 90,000 to 112,000 (Furuya et al., 2018b; Henderson and L eigh, 2012) . Estimates by Furuya et al. (2018 b) (Figure 14) suggested that the real figure may be as much as 255,000 deaths (243,223 to 260,029) of which 233,000 deaths (222,322 to 242,802) are occupational, with the greatest contribution from lung cancer, pa rticularly in HICs. Other diseases made a comparatively small contribution to global mortality from occupational exposure to asbestos, with approximately 2,000 in each of UMCs and LMCs, and less than 300 in LICs. 02,0004,0006,0008,00010,00012,00014,00016,00018,000 HIC UMC LMC LICNumer of deaths Reported Asbestos adjusted Continent- adjusted Employment-adjusted 26 Figure 14: Globa l deaths from all diseases as a result of occupational exposure to asbestos; data from Furuya et al. (2018b) . Abbreviations : high -income country (HIC); upper -middle - income country (UMC); lower -middle -income country (LMC; low -income country (LIC). As of July 2019, 67 countries have banned asbestos (Kazan -Allen, 2019b) , yet it is likely that the pandemic of asbestos related deaths is likely to continue to increase in the future despite apparent reductions in some countries , such a s Sweden and the Netherlands which were some of the early countries to ban asbestos in the 1970s (Stayner et al., 2013) . The analysis by Furuya et al. (2018b) indicated that deaths may at least continue at the same rate while acknowledging that the lack of data in LIMICs makes these kind of predictions challenging. Nonetheless, while countries such as India continue to permit unabated consumption of asbestos, it is likely that the death rate from asbestos exposure will continue to rise. It has been predicted that of the 1.25 million people who are expected to suffer from asbestos related cancer in the coming years, mo re than half will be in India (Jadhav and Gawde, 2019) . 3.5. Other particulate matter Collectively, construction and demolition activities are an important source of particulate matter (PM) emissions (Font et al., 2014) . In London (UK), for instance, co nstruction and demolition activities were estimated to contribute to 1.4% of total PM 10 emissions in 2010 (Font et al., 2014) and a study by Fuller and Green (2004) between 1999 and 2001 of over 80 sites across the city found that construction and demolition activities contributed to mean 163,989 38,561 17,556 2,216 - 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 HIC UMC LMC LICDeaths per annumAsbestosis Larynx cancer Ovarian cancer Lung cancer Mesothelioma 27 daily concentrations of >50 μg m-3 at 25% of the sites observed each year. This review has a specific focus on ‘construction waste’ and ‘demolition waste and activities ,’ ther efore ‘construction activities’ that do not involve waste are excluded. This presents a challenge in this section because most studies of PM emissions present data that is aggregated together with ‘construction’, ‘demolition’ and ‘construction waste’. Furt hermore, because this section focuses on mechanical (non -thermal) emissions of particulate matter, the scope is narrowed further to focus on emissions that arise when materials, such as ceramics, undergo mechanical attrition and aerosolisation. In layman’s terms, this section will discuss dust, defined variously as PM that is <75 μm or <100 μm in diameter (World Health Organization, 1999) . Two studies in the UK (Stacey et al., 2011) and Iran (Normohammadi et al., 2016) reported concentrations of total dust and respirable silica in and around demolition sites ( Table 9). The first, Stacey et al . (2011) visited 13 construction and demolition sites in the UK and found that the concentrations of respirable dust were not significantly different from background samples, except for the demolition activity which showed a significantly different concen tration ( p <0.001). Silica dust exposure is an increasing public and occupational health issue and is known to cause silicosis, a fibrotic disease of the lung (Leung et al., 2012) as well as b eing linked to lung cancer, pulmonary tuberculosis and other diseases as well as an indicative, but less studied, link with cardio -vascular diseases (Chen et al., 2012) . Nonetheless, although the time weighted aver age concentrations of respirable silica reported by Stacey et al. were higher during demolition activities, they were still far below the recently imposed absolute limit of 100 μg m-3 stipulated in Directive (EU) 2017/2398 (European Union, 2009) . Table 9: Concentrations of total dust and respirable silica in air around construction and demolition activities (μg m-3). Ref. Geog. Activity context Substance n Median Meana Min Max Stacey et al. (2011) GBR Urban air Respirable dust (ISO/CEN Convention) 11 17.5 34.4 General activities 9 24 17.4 29.5 Road building 10 29 24 41 Block cutting 7 35.1 17.5 76.9 Demolition 22 40.6 15.4 229 Urban air Non- combustible and non-volatile respirable dust 11 4.7 2.8 12.6 General activities 9 7.3 4.7 11.6 Road building 10 12.7 3.8 21.3 Block cutting 7 10.1 2.8 58.9 Demolition 22 10.1 1.7 186 28 Ref. Geog. Activity context Substance n Median Meana Min Max Urban a ir Respirable silica 8 0.24 0.08 0.44 General activities 9 0.19 0.08 0.39 Road building 10 0.64 0.11 1.04 Block cutting 7 1.2 (1.8*) 0.16 (0.33*) 11.9 (12.8*) Demolition 22 0.94 (2.1*) 0 (0.31*) 11.5 (13.5*) Normohammadi et al. (2016) IRN South Respirable silica 15 155 206 East 15 185 209 West 15 95 148 Centre 15 165 195 Total 60 155 206 South Total dust 15 14,990 5,000 28,000 East 15 11,860 5,200 18,000 West 15 11,930 5,600 28,000 Centre 15 14,680 11,460 20,790 Total 60 13,370 5,000 28,000 *Time weighted average; aarithmetic mean. Abbre viations: number of samples (n); geographical context (geog.); European Standards Organization (CEN); International Organization for Standardization (ISO). The The Air Quality Standards Regulations (2010) in the UK, require that particulate matter < 10 µm (PM 10) concentrations must not exceed 50 μg m-3 more than 35 times per year or an annual mean of 40 μg m-3. Although the PM 10 was not measured specifically, two of the concentrations for total dust measured by Stacey et al. (2011) were higher than 50 μg m-3, for block cutting and demolition ( Table 9). However, the majority were below the 50 μg m-3 threshold and although the average for the demolition site for respirable dust (define d as the portion of PM that is capable of reaching the alveoli – gas exchange sacs in the lungs) was slightly higher than the mean average concentration limit in the Air Quality Standards Regulations, the activity did not last for a year and therefore would not exc eed the threshold. The mean and median concentrations of respirable silica measured by Normohammadi et al. (2016 ) at a demolition site in Tehran, were approximately 100 and 200 times higher respectively than those observed by Stacey et al. (2011) (Table 9). All the mean concentrations identified by Normohammadi et al. exceeded the absolute limit of 100 μg m-3 stipulated in Directive (EU) 2017/2398 (European Union, 2009) , indicating that exposure to workers near these activities was possibly negatively affecting their health. Three further studies measured concentrations of PM in and around demolition sites in China, Germany and the UK ( Table 10), with many concentrations excee ding the threshold concentrations in Directive 2008/50/EC (European Union, 2008a) (Table S1 ). Liu et al. (2019) measured concentrations of PM 10 and particulate matter < 2.5 µm (PM 2.5) during and 29 following the demolition of a teaching building, finding elevated levels of bo th particle size profiles during the demolition process. It is worth noting that levels remained high after the demolition activities , indicating a very high background concentration in the area that exceeds the thresholds in Directive 2008/50/EC. Wagner et al . (2017) also found a considerable difference between PM levels during and after blast demolition of a skyscraper in Frankfurt, Germany, with maximum concentrations nearly 16 times greater than the limit value of 50 μg m-3. Both Liu et al. (2019) and Wagner et al. (2017) reported that atmospheric PM concentrations returned to background levels when demolition was not taking place, indica ting that the PM generated were either easily dispersed or deposited to the land. In the case of Wagner et al. (2017) , the PM cleared within 25 minutes , meaning that the daily average concentration only slightly exceeded the 24 hour lower threshold (25 μg m-3) for PM 10 stated in the Directive 2008/50/EC. Table 10: Concentrations of particulate matter ( PM) in air during construction and demolition activities (μg m -3). Ref Geog. Activity context Fraction n Mean* Min Max Liu et al. (2019) CHN a Demolition PM 2.5 296 94.409 b c 10.18 432.3 b c PM 10 156.521 d e 49.36 d e 495.4 d e After demolition PM 2.5 112 59.511 b c 10.01 189.24 b c PM10 92.881 d e 28.91 202.2 d e Wagner et al. (2017) DEU During skyscraper blast demolition (15 min) PM 10 844.9 d e Background (25 min later) 27.6 e Day average 32.6 e Azarmi and Kumar (2016) GBR Mobile sample collection (A) PM 1 12 4.7 2.2 8.3 PM 2.5 15.5 c 7.0 30.9 b c PM 10 162.7 d e 24.4 440 d e Mobile sample collection (B) PM 1 12 3.5 2.2 4.9 PM 2.5 7.5 3.3 12.2 c PM 10 37.2 d e 17.9 75.8 d e Inside excavator cabin PM 1 75 699 PM 2.5 109 b c 12 c, 401 b c PM 10 455 d e 54 e; 124 d e Inside temporary site office (normal) PM 1 8 26 PM 2.5 16 c 6 PM 10 90 d e 2,566 d e Inside temporary site office (during intense demolition) PM 1 56 338 PM 2.5 144 b c 114 b c PM 10 720 d e 549 d e;124 d e Fixed outdoor downwind of demolition activity PM 1 15.66 PM 2.5 60.19 b c PM 10 123.81 d e Exceeded the following concentration thresholds set by Directive 2008/50/EC (Table S1 ): a it is assumed that the site was in China from reading the paper, however the location wasn’t stated. b annual average upper assessment of PM 2.5; c annual averag e lower assessment of PM 2.5; d 24 hour average upper assessment of PM 10; e 24 hour average lower assessment of PM 10; *Arithmetic mean. Abbreviations : number of samples (n). 30 The study by Azarmi and Kumar (2016) took place over seven days and involved measuring concentrations in a variety of locations near to the demolition of a building, including static sampling sit es; inside a static portable office; inside an excavator and also mobile sampling around the site ( Table 10). Both the downwind and one of the mobile samplers showed levels of PM 10 that exceeded the 50 μg m-3 limit, as well as the 24 hour upper and lower limits. The levels in the excavator were 6.5 times higher than the fixed outdoor sampler exceeding the 50 μg m-3 threshold by nine times. Even more concerning were the concentrations at the temporary site office that reached levels of more than 14 times the threshold limit during a period of intense demolition. This finding is of particular interest, because speculatively, office environments are often considered relatively safe spaces on construction and demolition s ites and respiratory protection equipment is rarely worn inside . Azarmi and Kumar (2016) showed that the concentr ations were higher inside the office than anywhere else on the site, inferring a potential need for engineering controls and procedures to prevent the ingress of PM into the buildings. The relative contribution of demolition activities compared to constru ction and excavation activities was investigated by Arocho et al. (2014) who monitored air concentrations around two road resurfacing projects in the US ( Figure 15). The study showed a significant contribution from the demolition phase; accounting for 35% and 45% of PM in the two studies. While these data are highly specific to two projects in a US context, they provide a useful indication of emissions that can be used by healt h and safety risk planners to mitigate potentially harmful concentrations of atmospheric matter produced by their projects. Figure 15: Apportionment of PM emissions by project phase for two roadway reconstruction projects in the USA; after Arocho et al. (2014) . 4535 2343 107 168 67 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Little StreetWest Burkhead Demolition Earthwork Installation Paving Other 31 To assist future occupational safety planners further with the proactive management of risk, several authors have derived emissions factors for PMs emitted from various construction and demolition processes; data that are surprisingly scarce in the literature (Azarmi and Kumar, 2016) . Both Kumar and Morawska (2014) and Kumar et al. (2012) reported particle count from simulated concrete recycling and demolition processes respectively. The data are not presented here, but the studies focus on ‘ultra -fine’ part icles which the authors assert may pose significant health and safety hazards, and are a likely subject of further research. Azarmi and Kumar (2016) provide d more accessible emissions factors for PM 10, PM 2.5 and PM 1.0 based on their observations of the UK demolition site (reported in Table 10), providing indicative values on the basis of µg PM per floor space demolished per second ( Table 11). Table 11: Emissions factors (EF) for particulate matter ( PM) generated by demolition activities (µg m–2 s–1); after Azarmi and Kumar (2016) . EF PM10 EF PM2.5 EF PM1.0 Day 1 34.67 ±17.09 16.85 ±3.07 4.38±0.03 Day 2 36.05 ±8.15 17.52 ±4.32 4.56±1.07 Average 35.36 ±12.72 17.19 ±3.69 4.47±0.54 Abbreviations: p articulate matter < 10 µm (PM 10); particulate matter < 2.5 µm (PM 2.5); particulate matter < 0.1 µm (PM 0.1); emission factor ( EF). Few studies have carried out chemical characterisation of PM from demolition activities. Jiang et al. (2018) analysed dusts in Zhengzhou, China, and compared the geological and chemical profile with road dust, soil dust, and cement dust. By mass, the me an particle size across all samples was similar with approximately 10% (wt.) of the particles below 2.5 μm in all four samples. By particle count, the ≤1 μm was dominant, with 90% of all samples consisting of these ultrafine particles. Organic carbon (OC) <10 μm represented between approximately 5% and 12% of the mass, with concentrations of crustal element s and tens of elements detected. Two studies used particle emission characterisation to calculate occupational and public health risk. Normohammadi et al. (2016) used the concentrations of silica identified in dusts sampled in Tehran to calculate lifetime excess ca ncer cases from occupational exposure over 45 years. The study found that the concentrations identified in Table 9 would result in an average of 50 excess cancer deaths per 1,000 workers exposed ( Table 12). The study also calculated that the cumulative effect of silica exposure to workers in the study over 45 years 32 would result in a further 22.64 deaths per 1,000 people due to silicosis (data not shown) based on a cohort study of silicosis mortality by t Mannetje et al. (2002) . Table 12: Excess lifetime cancer deaths per 1,000 workers; after Normohammadi et al. (2016) . Area No. of samples GM (µg m-3) Excess lifetime risk of mortality from lung cancer (deaths per 1,000 workers) South 15 158 60 East 15 156 59 West 15 85 32 Centre 15 143 54 Total 60 132 50 Assumes 45 y ears of exposure at concentration specified. Abbreviations: geometric mean (GM); number of samples (n). Brown et al. (2015) identified PTEs in PM from demolition activities to calculate the risk to adults and children living nearby from selected elements ( Table 13). The analysis showed that the risk to children was >1 for aluminium and chromium. Table 13: Hazard index (HI) calculated for residents living near to demolition activities at a site in London, UK; after Brown et al. (2015) . Element HI - adults HI - children Al 0.711 1.132 Ba 0.005 0.039 Cr 0.528 1.079 Cu 0.009 0.062 Pb 0.039 0.099 Ni 0.004 0.033 V 0.015 0.103 Zn 0.004 0.024 This section has summarised relatively scant data on the risks associated with dust generated by demolition activities. These data sho uld be used by future researchers as a basis to develop a more detailed understanding of the risks resulting from dust generated by demolition activities . This is work that should be carried out as there is clearly an indication of risk to both the health of workers and of the surrounding population. 3.6. Substances from previous use of industrial premises The previous two sections have summarised evidence for emissions produced during the physical handling and processing of construction and demolition waste, relating to the actual materials used to construct buildings. However, there are also substances that arise from the 33 previous use of the buildings. This section briefly summarises two of these, pesticides and radioactivity that have contaminated sites and require consideration to protect the health of workers carrying out demolition activities. The first study, by Dugg an et al. (1974) is outside the temporal scope of this review; being published in 1974 . However , it is included here as an example of potential hazards as a consequence of substances arising in demolition waste as a result of previous use , rather than as part of the material fabric of the building. Duggan et al. (1974) sampled air at two facilities that had previously been used for radium luminising (production of luminous products) and a thorium extraction from monazite. Each factory contained radioactive dust as detailed in Table 14 and rather than clean the dust, the demoliti on operation involved breaking up and removing the entire concrete floor in each building. Table 14: Radioactive surface contamination in two United Kingdom ( UK) industrial buildings undergoing demolition; after Duggan et al. (1974) . Context Substance Units Apparent contamination per cm-2 Former radium luminising building Radioactive surfac e contamination 3.7 Bq 226Ra cm-2 7.4 Bq of β -ray emitters 7.4 Bq of α -ray emitters Former thorium factory 3.7 Bq 232Th cm-2 3.7 Bq of β -ray emitters Abbreviations: becquerels (Bq) As the concrete was agitated, much of the radioactive material be came aerosolised, exposing the unprotected workers. The air concentrations were determined using personal and static air samplers as detailed in Table 15. A stark difference was noted between the two plants that is explained by a defective jack -hammer being used in the Thorium extraction plant. Although the authors cite this as being ‘unfortunate’, it is a factor that may have reduced the probability of ill health in the workers over the proceeding decades. Duggan et al. (1974) concede d that had the jack -hammer been fully operable, the demolition workers may have required radiolo gical supervision following the activity. 34 Table 15: Concentrations of radioactive elements during demolition of two United Kingdom (UK) facilities that had previously processed radioactive materials; after Duggan et al. (1974) . Facility Activity context Dust loading (mg m-3) Concentration (Bq m-3) Specific activity (Bq g-1) Radium luminisi ng facility At start of hammering 38 0.555 14.43 41 0.481 11.84 During hammering 160 0.999 6.29 160 2.22 14.06 130 2.22 17.02 During hammering 100 4.44 44.4 400 3.219 8.14 390 3.219 8.14 Shovelling 14 0.185 13.32 80 0.296 3.7 75 0.999 13.32 50 0.666 13.32 Thorium extraction During hammering, outside 2 0.407 20.35 1-5 0-0.29 19.61 1-5 0-0.29 19.61 3 0.074 -0.333 35.89 4-5 0.111 -0.296 31.08 3-5 1.11 31.82 During hammering, inside 12 1.776 148 11 1.998 181.3 11 0.777 70.3 6 0.777 129.5 14 1.295 92.5 17 1.739 103.6 Two studies investigated concentrations of pesticides at disused manufacturing facilities in South -western Sweden (Van Praagh and Modin, 2016) and Northern China (Huang et al., 2016) (Table 16). Van Praagh and Modin (2016) found that although the concentrations of phenoxy acids, chlorophenols and chlorocresols were higher than Swedish soil guidelines for residential and industrial properties, they were far below the concentrations nec essary to be classed as hazardous waste. Leaching from the concrete occurred at a rate greater than inorganic substances and therefore the recycling of this concrete should be discouraged according to the study. 35 Table 16: Pesticid e concentrations in media at former pesticide manufacturing facilities. Ref. Geog. Waste analysed n Substance Mean conc. Low High SGV res.* SGV ind.* Van Praag h and Modin (2016) SWE Crushed concrete debris 4 Ʃ Phenoxy acids (PA) 8.5 Ʃ Chlorophenols (CP) 11.1 0.5 3 Ʃ Chlorocresoles (CC) 10.7 1.5 5 Ʃ PA, CP, CC 30.3 Huang et al. (2016) CHN Concrete coatings Brick Wood Detritus 32 0,0,0 -Trieth yl-phosphorothioate 288.5 UD 2,764 0,0'-Diethyl dithiophosphate 3,254 47.1 18,749 Phorate 16,868 112.9 82,327 Parathion 6,521 UD 67,807 Terbufos 170 UD 1,933 Ethion 53.3 UD 585.2 Chlorpyrifos 167.5 UD 1,919 Sulfotepp 80.8 UD 383.9 Cholrmephos 29 UD 692.1 Phorate sulfone 111.3 UD 3,163 Cypermethrin (Pyrethroid) 179.4 UD 3,155 a Organophosphorus and pyrethroid; * soil guideline values (SGV) from Swedish guidelines for residential (res.) and industrial (ind.) premises reported by Van Praagh and Modin (2016) ; abbreviations: number of samples (n); geographical context (geog.) ; concentration (conc.). Huang et al. (2016) analysed construction and demolition waste from a disused organophosphorus and pyrethroid pesticide production facility that had been closed for a decade. The study indicated that many of the concentrations were high and extremely severe, however the findings were not placed in context with other studies as it is challenging to do so because of the specificity of products. 3.7. Risk characterisation for handling and physical processing of construc tion and demolition waste The semi quantitative risk characterisation for the handling and physical processing of CDW is shown in Table 17. The highest risk was scored for asbestos exposure to workers in LIMICs. While the use of asbestos has been focused in HICs throughout the last century, consumption continues in LIMICs and the lack of stringency for protective equipment and safe systems of work indicates a much higher risk for workers in these countries. Workers in HICs were also scored high in this category as asbestos is still ubiquitous throughout the built environment and the probability of exposure is still considered high in several studies reviewed . HICS are not ‘over the hump’ yet. 36 The risk of physical acc ident in LIMICs is also scored medium high as there is evidence for a much higher accident rate and it is assumed that safe systems of work are generally less stringent and access to resources to reduce accidents less available. Particulate matter is also an important hazard that should not be overlooked though it scored medium low in all categories. One potentially overlooked risk is exposure to people working in po rtable offices who were exposed to extremely high levels of PM from demolition activities i n one study. This is important because workers in offices are less likely to wear protective equipment as it is often assumed that they work in a safe area. The risks from substances resulting from the previous use of a building have not been risk assesse d. These were included to indicate the harm but there is little evidence to suggest the prevalence of hazards or risks, though further investigation of this theme may be warranted. 37 Table 17: Risk characterisation summary for handlin g and physical processing (non -thermal) of construction and demolition waste (CDW). Haz. Pathway Receptor Geog. Evidence and justification for risk assessment Uncertainty (aleatoric and epistemic) Receptor vulnerability L S R Global receptor context Physical accident CDW handling Construction and demolition workers EUR  Eurostat (2020) provides some basic data on accidents involving ‘bulk waste’ under the NACE (economic) activity category for ‘construction and demolition’ indicating 6.14 accidents and 0.02 fatalities per 100,000 workers per annum.  Scant evidence from submissions to Eurostat with considerable underreporting due to method of data collection (Eurostat, 2019) .  Accidents or near misses that do not result in significant injury are not included in the statistics (European Commission, 2009) .  Most states do not or inconsistently report Phase III level of detail (Eurostat, 2010) .  In HICs workers are increasingly protected through safe systems of work, however there is eviden ce from Japan (Maeda et al., 2003; Takahashi, 2019) that good health and safety culture is not synonymous with HIC status and may be cultural. na na na HIC LIMIC Physical accident Demolition activities Demolitio n workers JPN, EUR, AUS, TUR, GBR  Evidence indicates fatalities in the demolition sector represent between 0.71 (European Commission, 2009) (EUR) and 7.5% (Maeda et al., 2003) (JPN) as a proportion of injuries from all sectors and accidents represent 0.16% in the EU only. For accidents and fatalities combined, data from AUS (Zaharuddin et al., 2009) indicate demolition represents 0.4% as a proportion of injuries from all sectors.  As a proportion of all construction and demolition, activities, fatalities range from 6.5% in J PN (Takahashi, 2019) , 3.8% in TUR (Gürcanli and Müngen, 2013) and 1.09% in EUR (European Commission, 2009) .  Injury rate as a proportion of all construction and demolition activities range from 3.9% in TUR (Gürcanli and Müngen, 2013) to 1.23% in EUR (European Commission, 2009) .  Very limited global data, limited to JPN and EUR.  Scant evidence from submissions to Eurostat with considerable underreporting due to method of data collection (Eurostat, 2019) .  Accidents or near misses that do not result in significant injury are not included in the statistics (European Commissio n, 2009) .  Most states do not or inconsistently report Phase III level of detail (Eurostat, 2010) .  Challenging to put accident and fatality data into context as not reported as a proportion of workforce.  In HICs workers are increasingly protected through safe systems of work, however ther e is evidence from Japan (Maeda et al., 2003; Takahashi, 2019) that good health and safety culture is not synonymous with HIC status and may be cultural. 2 4 8 HIC 3 4 12 LIMIC Asbestos Construction and demolition activities/inhalati on Construction and demolition workers Global  Though production and consumption have decreased over recent decades, huge quantities remain in the use phase, meaning that asbestos will remain a hazard for many decades to come. Though Brazil has now ceased production (Flanagan, 2020) , Russia, China and Kazakhstan continue and consumption of cement bonded chrysotile continues in 39 countries in 2017 (National Minerals Information Center, 2018) .  Strong data on mesothelioma deaths, however other diseases are estimates (Driscoll et al., 2005; Odgerel et  Considerable work has been carried out to estimate death as risk based on more than 100 cohort studies (Concha -Barrientos et al., 2004) and a considerable body of evidence is being compiled all the time.  Few studies have estimated non - mesothelioma de aths which are often challenging to attribute (Furuya et al. , 2018b) and therefore there is some uncertainty until further estimates have been carried out.  While workers in HICs theoretically have safer systems of work and better access to PPE, HICs have much greater historical consumption of asbestos synonymous with their level of construction activity during the 20th century. 3 4 12 HIC  Workers in LIMICs may be less aware of the potential hazards posed by asbestos and have less access to 4 4 16 LIMIC 38 Haz. Pathway Receptor Geog. Evidence and justification for risk assessment Uncertainty (aleatoric and epistemic) Receptor vulnerability L S R Global receptor context Population al., 2017; Vanya et al., 2011; World Health Organization, 2019) .  125 million estimated to be exposed (Spasiano and Pirozzi, 2017) and fatalities from all sources estimated at approximately 90,000 (Henderson and Leigh, 2012) ; 112,000 (Furuya et al., 2018b) ; 255,000 of which 233,000 are occupational (Furuya et al., 2018b) . PPE and safe systems of work in comparison to HICs.  Asbestos consu mption continues unabated in many LIMICs.  Countries such as India continue to permit unabated consumption of asbestos and it has been estimated that half of all asbestos related deaths will occur in the country in the coming decades (Jadhav and Gawde, 2019) . 1 4 4 HIC LIMIC Other PM Construction and demolition activities/inhalati on Construction and demolition workers IRN, GBR, DEU, CHN  Variable concentrations detected by studies depending on activity that was often not reported in enough detail to make a generalised assessment of risk.  High concentrations detected at some sites in Iran (Normohammadi et al., 2016) , but much lower in GBR (Stacey et al., 2011) .  Possible under -assessed ri sk in non -operational areas of construction and demolition sites such as offices which showed very high concentrations during intense demolition activity (Azarmi and Kumar, 2016) .  Also evidence that PM levels retur n to normal soon after intense demolition / blast demolition (Liu et al., 2019; Wagner et al., 2017) .  Quantified risk unacceptable and for exposure to Al (1.132) and Cr (1.079) by children in one study (Brown et al., 2015) but below 1 for all other elements and below 1 for adults for all elements.  Evidence (Arocho et al., 2014) that considerable proportion of emissions in road reconstruction are attributable to the demolition phase in comparison to the whole project.  Data generali sable but PM emi ssion from demolition activities are process dependent and therefore spot sampling may not be applicable to all activities .  In HICs workers are increasingly protected through safe systems of work, however there is evidence from Japan (Maeda et al., 2003; Takahashi, 2019) that good health and safety culture is not synonymous with HIC status and may be cultural. 2 3 6 HIC  Both formal and informal workers often operate without respiratory protective equipment. 3 3 9 LIMIC Population  Adults and children have no choice to avoid exposure if they live near construction and demolition activities. 2 3 6 HIC LIMIC  Children have no choice to avoid exposure if they live around construction and demolition activities. 3 3 9 HIC LIMIC Abbreviations: Likelihood (L); severity (S); risk (R); personal protective equipment (PPE); low income and middle income countries ; high income countries (HIC) ; particulate matter (PM); European Union (EU). 39 4. Challenge 2: Land disposal of construction and demolition waste (CDW) 4.1. Context The majority of CDW by mass is composed of biologically inert materials such as ceramics, plastics, and metals. Although inert to biota, some of these materials contain substances that can migra te to the surface and into surrounding media such as water or soil. For instance, polybrominated diphenyl ethers (PBDEs) that have been added to plastics to retard combustion are known to migrate from their host polymer to the surface from where they can be washed away by rainwater and into the surrounding land, ground or surface water. Biological materials may also exhibit similar migration properties, and in addition, have the potential to decompose, releasing gasses, chemical and biological residues that are created while being consumed by micro -biota. This section covers the evidence that relates to emissions of substances into the environment from the disposal of CDW on land, exploring the pathways that result in these substances interacting with enviro nmental and human receptors as illustrated in the conceptual diagram in Figure 16. Figure 16: Hazard exposure conceptual model (source –pathway –receptor) associated with disposal of constru ction and demolition waste (CDW) on land. Sources Migration to the surface of material via thermodyna mic equilibrium Adult citizens Pathways Receptors Groundwater Rivers, streams and lakes Surface water Receptor Route of human exposure Environmental compartment Substance or material Transfer process Legend Substances present in building materials Substances from previous use of building Mouthing Child citizens Ingestion Food Attenuation Leaching Soil Uptake in crops Drinking water Ingestion Co-disposed materials Bio-degradation Gas production Disposal site workers (form al) Disposal site workers Inhalation Building materials 40 4.2. Leachate from CDW Understanding of the characteristics of leachate from CDW when disposed of on land is important to determine the risk of exposure to environmental receptors. Leachate from CDW in HICs is often c ontrolled under strict legislation, and collected and treated on -site to prevent it escaping into the surrounding land and water (European Union, 1999; United States Environmental Protection Agency, 2000) . However in LIMICs, especially scenarios where open dumps are the main disposal method, leachate is often not controlled at all and may be at risk of interacting with sensitive receptors in the vicinity or further afield through water transport. Studies of leachate are either field based, or simulated in the laboratory, the latter of which is often carried out to determine whether waste is suitable f or disposal prior to actually doing so. López and Lobo (2014) samp led leachate at a CDW Spanish landfill site over a five year period that accepted mainly wood (31.5%), aggregates (28%), fine inert material (14.5%), plastics (6.7%), and inert building material (5%) along with many other materials produced as a consequenc e of construction and demolition activities. Concentrations of most substances in the leachate were mostly within limits for inert waste set by the Directive 1999/31/EC (European Union, 2002) (Landfill Directive) for waste acceptance ( Table 18). While the Directive limits are intended to establish waste acceptance and are not designed for comparison with field analysis, they provide a useful comparison alongside other primary research for reference. Some elements showed higher concentrations than those set in the Directive. Fo r instance , Pb was historically used in paints, coatings, and is still used in flashing and caulks. Mean concentrations of Pb were much higher than the levels in studies by Townsend et al. , Weber et al. , and Melendez, 6.5 times higher than the Directive li mit but lower than the U nited States Environmental Protection Agency (USEPA) study. 41 Table 18: Leachate quality from field samples collected from CDW landfill sites; field sample test from primary research by López and Lobo (2014) alongside compared values from other studies reported by the sa me author . Parameter Units López and Lobo (2014) USEPA (1995)* Melendez (1996)* Townsend et al. (2000)* & Weber et al. (2002)* European Union (2002) Field samples Field samples Field samples. Range from lit rev. C&D leachate. Field samples Directive 1999/31/EC Mean Range Mean Range Mean Range Mean Range (L/S ratio 0.1) pH 7.5 6.8-8.3 6.2-8 6.95 4.45-8 6.9 6.1-7.9 DO mg L-1 1.0 0.3-2.1 0.5 0.06-1.58 Conductivity mS cm-1 8.3 5.8-11 -1.67 1.1-3.1 ORP mV -89 -407/392 <-200 Total COD mg L-1 1,571 775-4,641 11,200 755 115-700 Dissolved COD mg L-1 1,407 586-4,190 Total BOD 5 mg L-1 227 70-500 320 87 Dissolved BOD 5 mg L-1 99 20-150 Dissolved TOC mg L-1 404 120-1,185 1,080 307 30,000 Alkalinity mg CaCO 3 L-1 3,189 1,800 -4,170 6,520 965 938.2 -6,520 530 210-960 NH 4_N mg L-1 401 92-765 305 13 <1-4.1 Dissolved TN mg L-1 463 182-844 Sulphates mg L-1 405 133-1,038 2,700† 254 11.7-1,700† 880 310-1,370 1,500 TS mg L-1 4,939 3,756 -577 TDS mg L-1 4,860 3,412 -576 8,400 2263 990-8,400 2,120 970-3,310 TVS mg L-1 1,619 1,208 -247 170-380 VSS mg L-1 75 5-781 43,000 As mg L-1 0.233† 0.048 -0.724† 0.12† 0.0123 0.0014 -0.0773† 0.0438 <0.01 -0.148† 0.06 Ca mg L-1 150 28-608 600 270 90-600 470 225-690 Cd mg L-1 0.027† <0.002 -0.182† 2.05† 0.0319† ND ND 0.02 Cr mg L-1 0.105† 0.005 -0.25† 0.25† 0.25† 0.0178 0.006 -0.0749 0.1 Cu mg L-1 0.028 <0.001 -0.087 0.62† 0.0203 0.005 -0.620 0.092 0.0056 -1.74† 0.6 Hg mg L-1 0.0014 <0.002 -0.0043† 0.009† 0.009† ND ND 0.002 Na mg L-1 495 206-834 1,510 163 11-1290 42.8 18.8-100.3 Ni mg L-1 0.0059 <0.003 -0.152† 0.17† 0.02 0.030 -0.170† ND ND 0.12 Pb mg L-1 0.987† 0.043 -3.119† 2.13† 0.0088 0.0049 -2.13† 0.0041 <0.001 -0.0141 0.15 Zn mg L-1 0.276 0.021 -0.735 8.63† 0.657 0.433 <0.1-1.731† 1.2 * Reported secondary source by López and Lobo (2014) ; † exceeded waste acceptance criteria limit specified in Dir ective 1999/31/EC (European Union, 2002) for inert landfill w aste abbreviations: liquid solid ratio ( L/S ratio); number of samples (n) ; construction and demolition ( C&D ); not detected (ND); dissolved oxygen (DO); redox potential (ORP), total organic carbon (TOC), ammonia nitrogen (NH 4-N), total solids (TS), total vo latile solids (TVS), total suspended solids (TSS); volatile suspended solids (VSS); biochemical oxygen demand ( BOD 5); chemical oxygen demand (COD); total nitrogen (TN); liquid to solid (L/S). 42 Concentrations of As and Cd were also high in comparison to the other sites ( Table 18), and to the levels set by Directive 1999/31/EC (European Union, 2002) , the former of which has been used h istorically in wood treatments . Alkalinity was within the 7.4 -8.3 range as befits this type of material where dissolution of carbonates present in the CDW takes place. Ammoniacal -nitrogen (NH 4-N) levels were generally higher than the other studies compared, likely because of the very high levels of wood waste being accepted at the site. In the lab based samples, virtually all of the concentrations w ere well within limits set by Directive 1999/31/EC (European U nion, 2002) (Table 19). An exception is the levels of Pb determined by Devia and Suryo (2017) which were more than four times greater in some samples. The sampling took place in Indonesia and the author attributes the high levels to paint on chip plaster. Research by Saca et al. (2017) of waste obtained from a demolished steel plant investigated biologically inert CDW such as concrete, bricks and ceram ics, which are materials that are unlikely to contain large quantities of hazardous materials. In all cases, the concentrations determined by Saca et al. (2017) were low. Unsurprisingly, the concrete batches showed higher pH due to carbonate dissolution, whereas the brick waste was neutral. Sulphate concentrations were variable and not congruent with the material type. The likely source of sulpha te ions is gypsum plasterboard and therefore it is likely that the concentrations relate to material adhered to the surface or otherwise included in the samples from a demolished factory. Whereas the characteristics presented in Table 19 refer to data obtai ned from percolation tests, two other test s are common for determining leachate over six or twenty four hours using a liquid to solid ratios (L/S) of 2 L kg-1 and 10 L kg-1 respectively. Saca et al. (2017) performed these tests on demolition waste from a steel plant in addition to those whose results are presented in Table 19. As with the other tests, the concentrations of substances assessed by bo th Puthussery et al. (2017) and Saca et al. (2017) were well below limits set by Directive 1999/31/EC (European Uni on, 2002) (Table 20). One exception is chlorides, which were slightly higher in one test, indicating that the material may not be suitable for recycling as the chloride ions can threaten the stability of structures by leading to corrosion of steel reinforcing materials. The phenol index was also higher in four of the samples and Saca et al. (2017) postulated that these concentrations were related t o the previous use of the building where phenolic compounds are used in steel production. 43 Table 19: Chemical properties determined from simulated leachate tests on sampled of CDW. Parameter Units Wang et al. (2012)* Devia and Suryo (201 7) Saca et al. (2017) European Union (2002) CDW Demolition waste <10 years Demolition waste >10 years Concrete 1 Concrete 2 Bricks 1 Bricks 2 Mixture 1 a Mixture 2 a Directive 1999/31/EC (L/S ratio 0.1) Mean Range Range Range pH 6.4 6.1-6.9 10.84 8 7.45 7.18 12.34 10.18 Alkalinity mg CaCO 3 L-1 75-725 Sulphates mg L-1 191.6 -240 150.4 -220.3 123.46 575.3 486.44 723 49.38 303 1,500 Chloride mg L-1 24-30 20.5-55 4.25 4.96 42.25 13.47 3.55 3.55 460 Fluoride mg L-1 1.1-1.5 2.4-2.75† <0.1 <0.1 <0.1 0.37 1.25 0.37 2.5 Phenol index 1.2 <0.1 <0.1 <0.1 0.31† <0.1 0.3 TDS mg L-1 873-2010 As mg L-1 <0.004 0.01 0.01 0.02 0.01 0.005 0.013 0.06 Ba mg L-1 0.03 0.11 0.17 0.07 0.059 0.059 4 Ca mg L-1 274 Cd mg L-1 <0.001 <0.001 <0.001 0.001 <0.001 <0.001 0.02 Cr mg L-1 0.1 0.01 0.003 0.004 0.09 0.1 0.1 Cu mg L-1 0.12-0.2 0.2-0.35 0.3 0.2 0.07 0.19 0.157 0.085 0.6 Hg mg L-1 0.00005 0.00045 0.00005 <0.00005 0.00032 0.00005 0.002 Mb mg L-1 0.03 0.04 0.05 0.05 0.027 0.065 0.2 Na mg L-1 21-37 Ni mg L-1 0.03 0.01 0.01 0.02 0.028 0.012 0.12 Pb mg L-1 0.52†-0.65† 0.42†-0.6† 0.005 0.007 0.003 0.01 0.005 0.005 0.15 Se mg L-1 0.006 0.005 0.01 0.01 0.006 0.009 0.04 Zn mg L-1 0.47-0.55 0.8-0.87 0.03 0.05 0.05 0.04 0.039 0.03 1.2 * Reported secondary source by López and Lobo (2014) ; † exceeded waste acceptance criteria limit specified in Directive 1999/31/EC (European Union, 2002) for inert landfill waste; a mixture of concrete, bricks, tiles and ceramics; abbreviations: number of samples (n); total dissolved sol ids (TDS); liquid to solid ratio (L/S). 44 Table 20: Characteristics of leachate from batch tests on various CDW media units are mg kg-1, except pH and phenol index which are dimensionless. Puthussery et al. (2017) Saca et al. (2017) European Union (2002) CDW Concrete 1 Concrete 2 Bricks 1 Bricks 2 Mixture 1 Mixture 2 Dire ctive 1999/31/EC limit L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 L/S=2 L/S=10 pH 11.82 11.64 8.45 8.53 8.28 8.48 8.04 8.18 11.87 12.02 10.49 10.24 Fluoride 0.2 1 2 5.9 2.1 3.7 2.4 5.9 0.7 1 3.6 9.9 4 10 Chloride 4.2 5 4.2 14 85.2 85 27 5 7 5 1 14 550 800 Sulphate 344 626 454 543 190 255 462 517 142 375 593 † 612 560 1,000 Phenol index 2.2 † 3.7 † 0.1 1 0.2 1.5 † 0.2 1 0.7 7.3 † 1.1 † 5.9 † 0.5 1 As 0.01 0.003 0.06 0.02 0.01 0.05 0.05 0.16 0.01 0.08 0.01 <0.01 0.03 0.16 0.4 2 Ba 0.29 0.051 0.06 0.25 0.06 0.17 0.06 0.1 1 0.07 0.3 0.114 0.45 0.052 0.2 30 100 Cd 0.01 0 0.002 <0.01 <0.002 <0.01 <0.002 <0.01 <0.002 <0.01 <0.002 <0.01 <0.002 0.01 0.6 1 Cr 0.03 0.013 0.2 0.3 0.004 0.04 0.01 0.03 0.01 0.07 0.2 0.48 0.11 0.2 4 10 Cu 0.19 0.039 0.4 1 0.1 0.7 0.19 0.75 0.27 0.78 0.198 0.95 0.2 0.57 25 50 Hg 0.26 0.004 0.0001 <0.0005 <0.0001 <0.0005 <0.0001 <0.0005 <0.0001 <0.0005 0.00068 0.00002 <0.0001 0.0005 0.05 0.2 Mo 0.05 0.002 0.07 0.14 0.04 0.05 0.04 0.08 0.03 0.05 0.05 0.12 0.09 0.12 5 10 Ni 0.07 0.033 0.04 0.08 0.01 0.03 0.03 0.05 0.01 0.03 0.068 0.08 0.02 0.04 5 10 Pb 0.12 0.079 0.004 0.04 0.006 0.02 0.01 0.03 0.01 0.06 0.016 0.02 0.008 0.05 5 10 Sb 0.01 0.002 0.2 0.7 Se 0.01 0.001 0.006 <0.01 <0.002 <0.01 0.01 0.02 <0.002 <0.01 0.014 <0.01 0.008 0.01 0.3 0.5 Zn 0.46 0.303 0.06 0.26 0.05 0.34 0.06 0.21 0.08 0.52 0.104 0.39 0.09 0.56 25 50 † Exceeded waste acceptance criteria limit specified in Directive 1999/31/EC (European Union, 2002) for inert landfill waste : abbreviations: liquid solid ratio (L/S). Abbrev iations: number of samples (n); liquid to solid ratio (L/S). 45 In summary, the concentrations of elements and other parameters identified in both the field sampling ( Table 18) and the la b sampling ( Table 19 and Table 20) were low in most cases compared to the limits set by Directive 1999/31/EC (European Union, 2002) and also other sites. However, only studies of surrounding soil, surface and underground waste can determine the potential exposure to receptors in proximity to land disposal. Furthermore, the limits set by Directive 1999/31/EC relate to well managed European landfills that have undergone careful site selection and risks assessment to determine the risk of leachate contamination to the surrounding area and groundwater sources. In the context of LIMICs where such rigour may not have been applied, CDW may pose a more significant risk to the environment and health of the local populous. Further studies should f ocus on understanding the impact of CDW on environmental compartments in LIMICs to determine the credibility of these risks. 4.3. Wood Wood used in construction is often treated with biocidal agents to improve its properties with substances such as fungicides , preservatives, creosote, paint, varnish, oils, glues, resins, and stains (Environment Agency, 2017) . A large number of biocides have been used historically, several of which contain potentially hazardous and carcinoge nic ingredients , such as pentachlorophenol (PCP), an organic chlorinated compound (Freeman et al., 2006) creosote, a tarry black substanc e containing a complex mix of polycyclic aromatic hydrocarbons (Freeman et al., 2006) ; and chromated copper arsenate (CCA), a highly effe ctive, waterborne biocide (Morrell, 2006) . Preservatives in timber are released through several mechanisms that involve: biodegradation of the wood itself; transformation of the wood, and /or preservatives by biological and thermal activity; and desorption by thermodynamic equilibrium (Schiopu and Tiruta -Barna, 2012) . Once they have reached the surface of the wood, they may be volatilised, leached into surrounding liquids or attenuated into soil. Many studies into the environmental and health impacts of treated wood focus on the release and exposure of preservatives during the use phase, whereas there is comparatively scant i nformation on the after -use phase (Schiopu and Tiruta -Barna, 2012) . Koyano et al. (2019) analysed samples of demolition and recycled timber for the presence of four wood preservatives that are now known to be persistent organic pollutants, comparing concentrations to limits suggested by the Basel Convention Secretariat ( Table 21). Although 46 the Basel Convention concerns the transboundary movements of waste, the Secretariat publishes guidelines that defines whether waste has been managed responsibly, so called ‘environm entally sound management’ (Secretariat of the Basel Convention, nd) . To assist with determining whether waste contains concentrations of persistent organic pollutants (POPs), it publishes a threshold below which the content is con sidered ‘low’ and hence different treatment practices may be applied. These low POP content limits provide a useful benchmark for determining the potentially hazardous concentrations of waste. As shown in Table 21, Koyano et al. (2019) found low levels of POP wood treatments in all samples of wood compared to the Bas el Convention limits of: chlordanes (CHLs ) 50 mg kg-1 (Secretariat of the Basel Convention, 2017c) ; PCP 100 mg kg-1 (Secretariat of the Basel Convention, 2017a) ; and polychloronaphthalenes (PCNs ) 10 mg kg-1 (Secretariat of the Basel Convention, 2017b) . Of course, the samples analysed by Koyano are highly specific to one area in Japan and further research wou ld be required to determine whether these concentrations are representative of other contexts. Table 21: Concentrations of elements, polybrominated diphenyl ethers, and selected wood preservatives (mg kg-1 dry wt.). Ref. Geog. Was te media analysed n Substance Mean Range SD Koyano et al. (2019) JPN Recycled timber 45 Chlordanes (CHLs) <0.01 <0.01 -0.86 0.13 Pentachlorophenol (PCP) 0.025 <0.01 -3.0 0.5 Pentachloroanisole (PCA) <0.01 <0.01 -1.1 0.18 Polychloronaphthalenes (PCNs) 0.033 0.0012 -2.6 0.43 Demolition timber 55 Chlordanes (CHLs) <0.01 <0.01 -15 2.3 Pentachlorophenol (PCP) <0.01 <0.01 -0.20 0.026 Pentachloroanisole (PCA) <0.01 <0.01 -0.043 0.0057 Polychloronaphthalenes (PCNs) 0.003 0.00049 -0.036 0.011 Duan et al. (2016) CHN Wood from landfill 1 polybrominated diphenyl ether ( PBDE ) 0.000541 Carpenter et al. (2013) USA CDW wood n/a Arsenic 37.04 Boron 0.27 Cadmium 0.65 Chromium 55.13 Copper 3,227.42 Mercury 0.13 Nickel 0.18 Lead 259.10 Antimony 0.03 Selenium BDL Zinc 2.88 Abbre viations: number of samples (n); standard deviation (SD); construction an d demolition waste (CDW). 47 Two other authors determined concentrations of potentially hazardous substances ( Table 21). Duan et al. (2016) measured concentrations of brominated flame retardants in a variety of building materials, one of which was wood . Levels identified were six orders of magnitude lower than the Basel Convention’s recommended Low POP Content of 1,000 mg kg-1 (for sum of hexa -brominated diphenyl ether (hexa -BDE ), hepta -BDE, penta -BDE and tetra -BDE). Carpenter et al. (2013) reported concentrations of various elements in CDW wood from a variety of literature sources, however no commentary is provided as these levels were reported as emission factors. Gaskin et al. (2005) carried out leaching tests on engineered timber mulch to determine the concentrations of substances that might leach into and potentially contaminate land. The comparison with non -treated varieties showed little difference and leve ls of all substances were low enough to conclude that engineered timber studies is entirely suitable to be used as mulch. Table 22: Rainfall runoff chemical characteristics (mg L−1) from simulated 64 mm storm leaching wooden mulch; after Gaskin et al. (2005) USA. Waste media analysed n Substance 2002 2003 TCLP regulatory level Category Composition Mean SD Mean SD Engineered timber 60% OSB, 20% plywood, 10% I -joist, 5% laminated veneer lumber, and 5% southern yellow pine gluelam timbers 1 Barium 0.295 5 Pentachlorophenol ND 100 3 Total phosphorus 0.21 0.017 <0.18 Total nitrogen 8.19 0.53 0.92 0.54 BOD 154.9 7.0 9.26 6.03 Residential mix 30% EWP (in proportions listed above), 45% dimension lumber (in proportions listed above), and 25% finger -jointed studs. 1 Barium 0.299 5 Pentachlorophenol 0.83 100 3 Total phosphorus 0.13 0.047 <0.18 Total nitrogen 2.57 0.40 0.92 0.16 BOD 273.5 8.28 3.37 Dimension Lumber 100% Dimension Lumber 3 Total phosphorus 0.21 0.15 <0.18 Total nitrogen 0.50 0.30 0.64 0.036 BOD 209.8 67.5 29.66 36.46 Abbreviations: toxicity cha racteristic leaching procedur e (TCLP); number of samples (n); oriented strand board (OSB); biochemical oxygen demand (BOD); engineered wood products (EWP) . Jambeck et al. (2008) studied the leachability of As, Cr and Cu from CDW containing 10% (wt.) timber treated with chromated copper arsenate preservative ( Table 23). The study found that though the concentrations of Cu were not different to the control, that Cr and As levels were significantly (∝ = 0.05, p < 0.001) higher, indicating the need for vigilance in CDW landfills where leachate is not captured for treatment and where attenuation may risk contaminating sensitive receptors. 48 Table 23: Element content and leachability of 10% chromated copper arsenate ( CCA ) treated wood by mass in construction and demolition ( C&D ) debris (leaching column); after Jambeck et al. (2008) . Basis Parameter Units As Cr Cu Content New CCA -treated wood mg kg-1 1,390 ± 20.0 814 ± 52.4 1,450 ± 68.3 Waste CCA -treated wood 1,960 ± 27.7 1,340 ± 54.0 2,550 ± 48.0 Leachate concentration Min mg L-1 1.09 0.3 <0.004 Max 4.25 2.1 0.07 Total 2.26 1.34 0.007 Proportion leache d 1.14% 0.57% 0.006% Abbreviations: chromated copper arsenate (CCA) 4.4. Gypsum Calcium sulphate dihydrate, otherwise known as ‘gypsum ,’ is a soft mineral used in fertiliser, plaster and drywall plasterboard. Global mine production has grown steadily from approximately 10 million tonnes in 1940 to 160 million tonnes in 201 0 and this sustained growth rate is expected to continue in the near future alongside global population growth (Asakura, 2013; US Geological Survey , 2020) . As it is used to coat internal walls in many constructions, gypsum is liberally distributed throughout demolition waste where it exists as fragments and dust between 17% and 27% of the mass of CDW (Townsend et al., 2000) . Once it has been mixed, it is challenging to separate, and although some novel methods of separation have been suggested (Montero et al., 2010) , manual separation is often the only effective method (Asakura, 2013) . In situ, plasterboard (drywall) and rendered plaster are generally stable, and exist in buildings for many hundr eds of years. However in landfills or dumpsites, sulphate ions are leached from the gypsum when they become solubilised, and in combination with carbon (organic matter), water and a lack of oxygen (anaerobic environment) the conditions are created to allow sulphate reducing bacteria to flourish and produce hydrogen sulphide (H 2S) (Townsend et al., 2000) . H2S is colourless, smells of rotten eggs, and can be hazardous to human health if inh aled at sufficient quantity. H 2S can cause: eye and lung irritation (20 to 200 ppm); pulmonary oedema (250 to 500 ppm); serious damage to eyes, unconsciousness, amnesia and death after four to eight hours (500 ppm) (Guidotti, 1996) . The concentrations necessary to cause a fatality have been repor ted at 1,000 ppm (Asakura, 2013; Guidotti, 1996) and 2,000 ppm (Townsend et al., 2000) and there are incidences where landfill operators have bee n killed 49 after being overcome with H 2S fumes (Asakura, 2013) . The Health and Safety Executive (2020a) in the UK, sets an eight -hour time -weighted average workplace exposure limit of 5 ppm and a 15 minute exposure limit of 10 ppm. Townsend et al. (2000) published a major non -academic report that investigated H 2S production form drywall gypsum plasterboard in landfills in the US. This spurred two academic studies by Lee et al. (2006) and Yang et al. (2006) , who determined concentrations of H 2S generated from CDW leachate samples in field and simulated studies CDW samples in the laboratory respectively ( Table 24). The subsurface probes and landfill gas samples in the field studies observed average concentrations that breached the UK HSE long -term workplace exposure limits at nine of the ten sites investigated, and the short -term exposure limit at seven. The average amb ient concentrations were generally low in the study by Lee et al., indicating generally low risk to workers at the site with the exception of two sites where concentrations exceeded the limit of detection (>50 ppm) for the ambient sampling equipment. Both the sites that showed a very high limit disposed of fines from CDW recycling plants, which are known to contain higher than average concentrations of gypsum drywall fragments that are generally more friable and easily fall through the grate openings of ballistic separation equipment. Table 24: Concentrations of hydrogen sulphide (H 2S) produced by construction and demolition waste (CDW) in field sampled and simulated experiments. Ref Geog. Sample media Components n* Mean Med Min Max Lee et al. (2006) USA LF gas from sub - surface probes or gas wells CDW 19 26†‡ 0.013 BDL 470†‡ CDW 77 8.1† 0.007 BDL 920†‡ CDW 8 30†‡ 25†‡ 0.013 12,000†‡ CDW 25 2,110†‡ 1,800†‡ BDL 7,000†‡ CDW 62 36†‡ 0.02 BDL 2,500†‡ Class III 16 5.9† 0.004 BDL 49†‡ CDW 19 0.007 0.005 BDL 0.64 Class III 20 151†‡ 0.025 BDL 3,300†‡ CDW e 22 1,200†‡ 23†‡ BDL 11,000†‡ CDW e 26 26†‡ 0.35 BDL 530†‡ Total 294 660†‡ 0.023 BDL 12,000†‡ Ambient air at surface CDW 5 0.042 - 0.39 CDW 18 0.003 - 0.11 CDW 5 0.12 0.05 0.39 CDW 24 0.19 0.007 2.4 CDW 41 0.039 0.004 0.6 Class III 17 0.008 0.004 0.12 CDW 2 0.15 - 3.5 Class III 6 0.037 - 0.27 CDW e 23 4 0.61 >50†‡ 50 CDW e 21 2.7 0.008 >50†‡ Yang et al. (2006) USA Simulation Wood, drywall, concrete a 56 0.277 BDL 1.6 62 0.2 BDL 1.03 64 0.15 BDL 0.67 Drywall, wood b 73 14,075†‡ BDL 63,000†‡ 74 11,155†‡ 0.003 48,000†‡ Drywall c 73 21,636†‡ BDL 47,000†‡ 73 24,389†‡ BDL 50,000†‡ Wood, concrete d 37 0.13 BDL 1.5 †Exceeds long -term ( eight hour) exposure limit set by UK Health and Safety Executive (2020a) of 5 ppm; ‡exceeds short - term (15 min) exposure limit set by UK Health and Safety Executive (2020a) of 10 ppm; e these sites accept residues from CDW recycling facilities; class III facilities accept combined CDW, large non -putrescible items suc h as furniture and yard waste. Abbre viations: number of samples (n); landfill (LF); below detection limit ( BDL ); geographical context (Geog.); construction and demolition waste (CDW). The gas samples generated from simulated CDW studied by Yang et al. (2006) showed very high concentrations of H 2S in four of the eight samples investigated. The four samples that included concrete showed much lo wer overall decomposition, and subsequent studies (Xu et al., 2011) have indicated that the concrete has an inhibiting effect on H 2S pro duction due to its alkalinity. Sulphate reducing bacteria require a source of carbon, and despite the wood content in the concrete sample, H 2S production remained low. The samples that did not contain concrete produced high concentrations of H 2S including the purely drywall sample , which obtained enough carbon from the paper lining (typically 10% of the drywall mass ) (Yang et al., 2006) . Modern, well manage d landfill operators deposit gypsum in separate cells and capture and manage the landfill gas generated. Although no evidence was forthcoming, it is conceivable that CDW disposal practices in LIMICs are less rigorous, and that an increasing quantity of gypsum may be co -disposed with MSW in the future. As some landfill site and dumpsites in LIMICs are not restricted effectively from public access, H 2S generation could pose an increasing threat to human health and even cause further fatalities if management practices are not improved. 4.5. Hexabromocyclododecane (HBCD ) As one of the most widely used brominated flame retardants, hexabromocyclododecane (HBCD), is mainly used in expanded polystyrene insulation, an increasingly prevalent component of CDW (Nie et al., 2015) . In 2011 production was 31,000 tonnes worldwide; however, it has decreased in recent years as its persistence in the natural environment and potentially harmful health effects on humans and animals have become esta blished and 51 alternatives developed to perform the same function. HBCD is listed in Annex A of the Stockholm Convention (Secretariat of the Stockholm Convention, nd) , which means that parties to the convention must take steps to eliminate it from production and consumption; as well as Annex C, which obliges parties to control unintended release of the substance into the environment. As HBCD has been used in insulating material, it is likely to be in use for many decades and will therefore continue to arise in CDW. Similarly to HBCD, PBDEs include congeners that are persistent organic pollutants and cause harm to fauna. Duan et al . (2016) sampled CDW collected from a recycling facility in China to determine HBCD and PBDE concentrations, finding the highest in samples of polyurethane foam and sponge for both compounds compared to other samples by orders of magnitude ( Table 25). Drage et al. (2018) sampled expanded polystyrene (EPS) and extruded polystyrene (XPS) insulation found in construction waste in Ireland, finding high concentrations of HBCD in the XPS sample and extremely high concentrations in the EPS sample. Table 25: Concentrations of selected brominated flame retardants, and polychlorinated biphenyls (PCBs) in construction nd demolition waste ( CDW ) (mg kg-1 total solids) . Ref Geog. Sample media Components n* Mean Med Min Max Duan et al. (2016) CHN PUR foam insulating layer HBCD 1 0.1666 PUR foam floor mat 1 0.1105 Furniture 1 0.03 PUR foam and sponge 1 7.039 Remainder sample 1 0.0077 PUR foam insulating layer PBDE 1 0.2187 PUR foam floor mat 1 0.14994 PUR foam and sponge 1 79.766 Remainder of sample 1 0.00059 Drage et al. (2018) IRL Construc tion and demolition EPS ƩHBCD 62 2,100 100 <0.0003 10,000 ƩPBDEs <0.0003 <0.0003 <0.0003 <0.0003 BDE -209 <0.0008 <0.0008 <0.0008 <0.0008 Construction and demolition XPS ƩHBCD 27 19 <0.0003 94 ƩPBDEs <0.0003 <0.0003 <0.0003 <0.0003 BDE -209 <0.0008 <0.0008 <0.0008 <0.0008 Butera et al. (2014) DNK CDW from recycling facility ƩPCBs 33 17 Abbre viations: number of samples (n); construction nd demolition waste (CDW); expanded polystyrene (EPS) and extruded polystyrene (XPS); polyurethane (PUR); hexabromocyclododecane (HBCD ); brominated diphenyl ethers (BDE); polychlorinated biphenyls (PCB ); polybrominated diphenyl ethers (PBDE). While concentrations of brominated flame retardants and PCBs in leachate and groundwater were not identified in proximity to CDW activities in this study, the concentrations identified in Table 25 provide an indication that these substances exist in considerable quantity. As Nie 52 et al. (2015) point out, the prevalence of these substances and their persistence in th e value chain means that considerable attention will need to be paid toward managing these products safely in the future, particularly when it comes to land disposal. Furthermore, assuming the recycling of CDW becomes more common in the coming decades, the re will be a greater need to identify products containing PCDDs, HBCDs, PBDEs and PCBs and divert them to other forms of treatment for complete destruction. 4.6. Risk characterisation for land disposal of construction and demolition waste The risk assessment in Table 26 indicates generally low to medium risks from CDW when disposed of on land. In general, CDW is composed of biologically inert material. Some exceptions are the inclusion of gypsum plasterboard that can pr oduce hydrogen sulphide gas when co -disposed with small amounts of biological material; providing a source of carbon f or sulphate reducing bacteria to consume and produce the gas. Some wood preservatives may also pose a risk and one author cautions vigilan ce in scenarios where CDW is disposed in unlined and unmonitored landfills where it is assumed that the contents are generally inert and pose little th reat to the surrounding environment. This is particularly important for LIMICs where less stringent gover nance and monitoring may be implemented. HBCD was not assessed as it was considered negligible based on the evidence. 53 Table 26: Risk characterisation summary for land disposal of construction and demolition waste (CDW). Material Haz. Pathway Receptor Geog. Evidence and justification for risk assessment Uncertainty (aleatoric and epistemic) Receptor vulnerability L S R Global receptor context CDW general Misc. substances in an properties of CDW Leachate, groundwater, land Drinking water/ population USA, SPN, IND  Several studies (Devia and Suryo, 2017; López and Lobo, 2014; Puthussery et al., 2017; Saca et al., 2017) determined characteristics of CDW itself as well as leachate produce d from CDW in landfill finding generally low levels of potentially hazardous substances in comparison to limits set by Directive 1999/31/EC (European Union, 2002) .  Although evidence is presented of the levels of various substances in leachate, no data w as found that indicates the concentrations in environmental comp artments close to CDW disposal sites.  Inert landfills often have less secure liners as they are assumed to contain less hazardous material, in LIMICs they may have no liner at all or exist as open dumpsites. In these cases, local environmental receptors ma y be more vulnerable to exposure from potentially hazardous substances in leachate from disposed CDW. 1 2 2 LIMIC CDW wood Wood preservatives Leachate, groundwater, land Drinking water/ population USA, CHN, JPN  Preservative (POP) concentrations determin ed in samples of wood in one study in JPN (Koyano et al., 2019) to be very low; PB DE concentrations extremely low (Duan et al., 2016) and element concentrations ‘unremarkable ’ (Carpenter et al., 2013) .  Study of leachate from wood chip mulch (Gaskin et al., 2005) made with treated timer indic ated very low risk of transmission of hazardous substances into surrounding area  Study of leachate from chromated copper arsenate treated wood (Jambeck et al., 2008) indicates cause for concern if landfill leachate not treated or risk of attenuation to nearby sensitive receptors.  Limited data but indication of little cause for concern from wood leachate 2 3 6 LIMIC CDW gypsum Hydrogen sulphide gas Atmosphere/ inhalation Landfill/ dumpsite workers (formal) USA  Several studies determined H 2S production in simulated studies (Yang et al., 2 006) as well as in real word concentrations of landfill gas (Lee et al., 2006) , finding potentially very high concentrations in the simulated and landfill gas studies.  Examples exist where landfill workers have died when overcome with fumes from excessive concentrations of H 2S in the air, though ambient concentrations in one study were determined to be little cause for concern (Lee et al., 2006) .  The theoretical basis exists for H 2S production but the one available study of ambient concentrations reported them to be low. Further study is necessary to determine the credibility o f the threat posed by H 2S in CDW landfill specifically.  Many HICs have banned co - disposal of gypsum plasterboard. 1 3 3 HIC LIMIC Landfill/ dumpsite workers (informal)  Informal workers operate without respiratory protective equipment and may be un aware of the potential hazard from H 2S production.  Speculatively, in LIMICs, co - disposal of gypsum with organic material may be more likely 3 4 12 LIMIC Abbreviations: Likelihood (L); severity (S); risk (R); low income and middle income countries ; high i ncome countries (HIC); hydrogen sulphide (H 2S); persistent organic pollutants (POP); construction and demolition waste (CDW); polybrominated diphenyl ethers (PBDE). 54 5. Challenge 3: Thermal deconstruction and processing of construction and demolition waste (C DW) 5.1. Context Several thermal processes take place on construction and demolition sites. Materials may be combusted in the open (open burning) as a means of waste disposal, resulting in uncontrolled emissions of substances within materials and also those th at are formed and transformed when substances and materials interact during combustion and various temperatures. Other thermal processes involve more incidental emission of substances. For instance steelwork on a surface coated in lead paint, or paint de -coating with a heat gun. These processes, the emissions that result and the pathways through which these emissions may reach receptors are illustrated in the conceptual diagram in Figure 17. Figure 17: Hazard exposure conceptual model (source –pathway –receptor) associated with thermal deconstruction and processing of construction and demolition waste (CDW). Sources Released during combustion Dust Atmosphere Food Inhalation Child citizens Adult citizens Occupational (formal) Mouthing Pathways Receptors Building materials Soil Ingestion Deposition Groundwater Rivers, streams and lakes Surface water Sediments Ash Uptake in crops Products of incomplete combustion Receptor Route of human exposure Environmental compartment Substance or material Transfer process Legend Released during thermal deconstruction Substances present in building materials Substances from previous use of building 55 5.2. Lead release during deconstruction activities The dangers of lead (Pb) exposure are w ell established and there is evidence that the potential hazards from Pb have been known for thousands of years (Scholz et al., 2002) . In CDW, Pb occurs in soldered plumbin g, but mainly in paints and coatings where Pb has been added to accelerate drying, increase durability, maintain a fresh appearance and resist moisture. Though Pb is still used in road markings, its potential hazardousness has seen the substance phased out of use in recent decades, however it still exists almost ubiquitously throughout the built environment. For instance, Turner and Solman (2016) analysed paint samp led (n=272) from multiple public buildings, road markings, street furniture, children’s playgrounds, and residential buildings in Plymouth, UK, finding it was present in 221 (81%) of the samples with a mean concentration of 29,300 μg g− 1 and a median of 4,180 μg g− 1. In 1998, Jacobs (1998) reported that in the US, more than 90,000 bridges were painted in lead -based coatings and approximately 83% of residential homes constructed before 1980. These findings indicate the prevalence of Pb almost everywhere people live, however there is some evidence that it is still being used. For instance Gottesfeld et al. (2013) analysed 61 samples of paint i n Cameroon and found that 66% contained concentrations of Pb that exceeded United States Environmental Protection Agency ( USEPA ) 90 ppm total Pb with a median content of 2,150 across the samples (range: <21 -500,000 ppm). While there is considerable awarene ss of the dangers of Pb in HICs, and in many LIMICs, construction and demolition workers in LIMICs may have less awareness and have limited access to safe systems of work and protective equipment to protect them from the potential hazards posed by Pb when it is heated and volatilised during deconstruction activities. The Health and Safety Executive (2009) in the UK, defines a ceiling workplace exposure limit 150 µg m-3 (‘lead other than lead alkyls’). Jacobs (1998) reported a range of Pb concentrations in workplaces in the US from secondary sources, showing a large range of concentrations reported ( Table 27), many of which exceeded the HS E occupational exposure ceiling limit of 150 µg m-3. Scholz et al. (2002) also found similarly high limits in a study of paint workers who removed Pb pain t during refurbishment activities. In another study by Lange and Thomulka (2000) much lower concentrations were identified in a study of workers who implemented US OSHA procedures in their work , indicating that they were effective at reducing their exposure. 56 Table 27: Concentrations of Pb measured in air proximate to deconstruction workers (µg m- 3). Ref Geog. Activity context Receptors n % n Mean Range Jacobs (1998) USA Wrecking and demolition a Demolition workers 178 14% <1 18% 1-99 10.7% 100-200† 57.3% >200† Bridge rehabilitation b Torch burner 220†-6,000† Hammering and drilling 40-360† Bridge demolition b Torch burner 110-1,200† Burner helper 330† Torch burner 180†-1,800† Rivet removal 500†-930† Paint removal from boiler b Blaster 640†-1,400† Power plant demol ition b Torch burner 2,100†-22,400† Bridge repair b Welder 2,200†-4,200† Blaster 1,070†-10,400† Burner 840-4,900† Paint removal from bridge b Blaster 4-540 Groundsman 20-640 Blaster 2-730 Bridge demolition b Burners 600-4,000† Paint re moval from bridge b Blaster 3,690†-29,400† Groundsman 5-6,720 Scholz et al. (2002) USA Residential and commercial painting Heat gun 6 2.3 <1 (n.d. ) - 5 Wet sanding 3 3.3 <1 (n.d.) - 7 Open flame burning 5 9.8 <4 (n.d.) - 20 HEPA -exhausted power sanding 7 33 4 - 60 Dry scraping 18 71 <4 - 230 Dry manual sanding 9 420† 29 – 1,200† Uncontrolled power sanding 10 580† 65 – 3,400† HEPA -exhausted power sanding 7 1,600† Dry scraping 17 1,100† Dry sanding 9 6,700† Uncontrolled power sanding 10 14,000† Lange and Thomulka (2000) USA Burning and cutting of pipes and removal (demolition) of walls that were painted No wet methods for cutting 5 379.6† 194-571† (122.1) 36 31.9 1.3-119 (11.0) No wet methods for burning 5 27.1 8.2-39.5 (13.5) Wet methods for cutting 8 7.8 4.7-10.6 (1.7) No wet methods for cleaning 1 60.8 Total for all samples 57 61.1 1.3-571† (29.4) † exceeds HSE limit of 150 µg m-3 for Pb concentration in atmosphere; abbreviations: number of samples (n); high efficiency particulate or arrestance (HEPA ); geographical context (geog.). Blood concentrations of workers involved in deconstructi on activities were determined by several authors. Fischbein et al. (1978) found concentrations of Pb in the blood of steel deconstruction workers to be higher in some cases than the HSE maximum limit set at 600 µg 57 L-1 blood. Centers for Disease Control and Preven tion (1989) found very high concentrations in the blood of workers deconstructing a steel bridge, noting that the paintwork on the bridge contained 30% Pb (wt.). Four of the workers in that study had to undergo chelation therapy to recover from the experi ence. Table 28: Concentrations of elements in blood of workers engaged in deconstruction Ref Geog. Activity context Receptors n Mean (µg L-1) Range Fischbein et al. (1978) USA Deconstruction of elevated steel subway Demolition workers 11 460 320-710† Centers for Disease Control and Prevention (1989) USA Deconstruction of steel bridge Demolition workers 5 780† 670† 580† 740† 1,600† Jacobs (1998) USA Lead based abatement work Demolition workers 1 40-150 1 30-180 1 30-100 1 40-180 1 40-<100 1 50-60 1 20-<100 1 50-60 1 100-290 1 50-100 † exceeds HSE limit of 600 µg L-1 for Pb concentration in blood; abbreviations: number of samples (n) ; geographical context (geog.) . It is noteworthy that most of the studies reviewed in this section relate to HIC examples from several decades ago. Workplace safety has improved considerably in HICs since these studies took place and awareness of the dangers of Pb at work ha s increased to the level where many workers have safety systems of work in place to protect them from harmful exposure. However in LIMICs, as with many hazards, such safety measures may not have been implemented with the same stringency , therefore resulting in ongoing and considerable risk to those engaged in thermal deconstruction of steel structures and in the removal of paint. 5.3. Combustion of CDW The combustible fraction of CDW is a potential source of fuel, which in LIMICs may be utilised by those engaged in demolition or construction activities. If fuel isn’t required, then alongside dumping and storage, combu stion is a common disposal option (Nie et al., 2015) as it can rapidly reduce the volume and mass of waste, discharging the problem to the 58 atmosphere. The prevalence of the activity isn’t well reported , but surveys of Nig erian construction workers indicate 2.9% (n=243) (Ogunmakinde et al., 2019) , and 16% (n=75) (Wahab and Lawal, 2011) of construction practitioners engage d in open burning activities as a method of disposal . Furthermore , construction wood that is sold for reuse as suggested by Dania et al. (2007) is often burned as fuel, though the prevalence was not stated. Combustible components of CDW include : wood, plastics, foam insulation, plastics, yard waste. Emissions from open burning of waste have been modelled extensively by Wiedinmyer et al. (2014) and (Kodros et al., 2016) . Lemieux et al. (2004) stated that open burning of CDW is likely to be a prevalent activity but suggested that there is little evidence to support its prevalence or impact. Instead , they suggested a study by Carroll (2001) that characterises polychlorinated dibenzo -p-dioxins (PCDD) and polychlorinated dibenzofur an (PCDF) (hereafter dioxins and related compounds – DRCs) emissions from house fires as the composition of the material has some congruence with CDW. Carroll (2001) provide d a comprehensive review of emission factors for various wood produ cts, demolition and construction wastes and plastics used in construction such as polyvinyl chloride ( PVC ) piping ( Table 29). PVC is used increasingly on construction sites and a priori data suggest s that it may occ ur increasingly in demolished buildings as its use becomes more prevalent. The chlorine content in PVC means that production of DRCs is considerably higher ( for example, 3,500 µg I -TEQ t-1 in soot phase) than other combustible components of CDW ( for exampl e, waste wood 26 -173 µg I -TEQ t-1 in vapour phase). Table 29: PCDD/F emissions factors for selected products used in CDW; after Carroll (2001) . Secondary ref. Sample Phase Emission factors (µg I -TEQ t-1) Theisen et al. (1989) Soft PVC Soot 230 Hard PVC 3,500 Fibres 600 Ikeguchi and Tanaka (1999) Electrical wire tube 1,032 Vikelsoe and Johansen (2000) PVC resin 100 PVC resin 3 Merk et al. (1995), Merk (2000) PVC/wood 750-2,250 Schatowitz et al. (1994 ) Waste wood Air 26-173 Ikeguchi and Tanaka (1999), Ikeguchi (2000) Construction waste 92 Demolition waste 26 Schatowitz et al. (1994) Beech Vapour 0.44-0.50 Chips, chipboard 0.007 -0.15 Waste wood 0.7-29 Schramm et al. (1998) Treated wood pi eces, boards 15-40 59 Secondary ref. Sample Phase Emission factors (µg I -TEQ t-1) Treated wood pieces, beams 2.4-6.6 Kolenda et al. (1993) Blocks, plywood, residues 3.5-11 Chopped wood briquettes 4.9-7.0 1.4-6.3 Launhardt et al. (1996) Beech, conifer 0.035 -0.13 Abbreviations polychlorinated dibenzo -p-dioxins and polychlorinated dibenzo -p-furans (PCDD/F); polyvinyl chloride (PVC); toxic equivalency ( I-TEQ ) When wood that has been treated with preservatives is combusted, the potential exi sts for some chemical species to be produced in addition to those a lready created because of combustion of the wood itself. For instance, PCP, an organochlorinated compound used in many pressure treated timber products since the late 1950s contained DRCs formed at the time of production ( Table 30). Table 30: Concentrations of DRCs in selected wood products treated with pentachlorophenol (PCP); after Swedish Environmental Protection Agency (2009) . Product TEQ ng g-1 Ky-5 treate d wood 38 Wood used in agricultural application 0.016 -315 Sawmill waste landfill 0.067 Utility pole, freshly treated, 1996 3.1 Utility pole, freshly treated, 1999 6.8 Utility pole after 1 years' use 15 Utility pole after 4 years' use 14 Utility po le after 11 years’ use 6.3 Utility pole after 24 years' use 7.7 Utility pole after 34 years' use 0.71 Abbreviations: toxic equivalency ( TEQ ) All chlorinated hydrocarbons have the potential to produce DRCs when combusted , including untreated timber. If combustion is controlled, for instance in modern incinerators, dioxin production is limited by maintaining optimum temperatures to reduce formation and increase the potential for destruction. Emissions cleaning technology is able to capture the majority o f DRCs before the remaining (circa 1%) are released to the atmosphere where they are diluted into the environment. However in open burning, no such controls exist, and although temperatures in some parts of the fire may be sufficient ( for example, >850°C ) (Wielgosiński, 2011) to reduce formation, other parts will facilitate conditions ideal for DRC formation and release (Tame et al., 2007) . 60 CCA is another important woo d preservative that entered the global market in the 1940 s and became the most globally prevalent preservative used in wood treatment during the 1970s (Wasson et al., 2005) . The high content of three potentially to xic elements Cr, Cu and As results in their emission into ash and air during combustion. Wasson et al. (2005) characterised emissions from combustion of wood treated with several CCA formulations, finding very larg e concentrations of As, Cr and Cu in the fly ash ( Table 31). Table 31: Concentrations of elements in soot from combustion of chromium copper arsenate (CCA) treated timber; after Wasson et al. (2005) . Element Formulation 1 Formulation 2 Formulation 3 As 116,500 111,350 129,300 Ca 200 7,600 3,510 Cl 110 270 190 Cr 980 29,500 12,000 Cu 1,060 17,800 6,710 K 740 2,810 1,730 Na 60 1,240 1,050 P 70 340 140 S 740 1,160 480 Unidentified 838,000 757,000 791,100 Emission factors for As, Cr and Cu were also calculated by Wasson et al. (2005) and are presented in Table 32, however it is noteworthy that the emissions of DRCs reported in the same study were ‘unremarkable ’ with mean concentrations of 1.7 ng TEQ kg-1. This indicates that the CCA treatment doesn’t significantly contribute to DRC formation. Table 32: Emission factors for Cr, As and Cu from chromium copper arsenate (CCA) treated timber (mg kg-1 CCA treated wood); after Wasson et al. (2005) . As Cr Cu Sample 1 188 22 9.8 Sample 2 218 14.9 13.4 Sample 3 237 8.4 8.7 In general, data on the open burning of CDW are extremely limited . It is a recommendation of this report that considerable additional work is carried out to determine the prevalence of this activity and also to determine the relativ e emissions of different material composition to assist with the improved compilation of a global inventory. 61 5.4. Risk characterisation for thermal deconstruction and processing of construction and demolition waste The semi -quantitative risk assessment for the rmal deconstruction and processing activities is shown in Table 33. Very high scores were attributed to the risk to both construction and demo lition workers in LIMICs as well as the population who may be expos ed to the activities. There is still limited information in this area on the prevalence of CDW open burning and more data are urgently needed to assess the magnitude of the threat to human health. Exposure to lead was scored low in HICs mainly because the danger s are well established and safe systems of work have been in place, often for many decades. In LIMICs the score was medium high as although the dangers are known, the governance, enforcement and access to resources required to reduce exposure may not be in place; acknowledging that no evidence was found to determine direct lead exposure from CDW in LIMICs in this study. 62 Table 33: Risk characterisation summary for thermal deconstruction and processing of construction and demolit ion waste (CDW). Haz. Pathway Receptor Geog. Evidence and justification for risk assessment Uncertainty (aleatoric and epistemic) Receptor vulnerability L S R Global receptor context Pb Thermal deconstruction of steel structures and removal of paint Deconstruction workers USA  Pb exists in coatings throughout the built environment (Jacobs, 1998; Turner and Solman, 2016) and without adequate precautions could pose risk to deconstruction workers for many dec ades to come (Scholz et al., 2002) .  The evidence for aerosolisation of Pb from thermal deconstruction of steelwork and paint removal is strong (Jacobs, 1998; Scholz et al., 2002) , as is the effectiveness of safe systems of work a t reducing atmospheric concentrations (Lange and Thomulka, 2000) .  A clear link between thermal deconstruction activities and blood Pb levels exists and therefore it is clear that adequate pre cautions should be taken.  All the studies (Jacobs, 1998; Lange and Thomulka, 2000; Scholz et al., 2002) were in the USA and several decades old. No data was found to determine risk in LIMICs other than Pb is still being used in paint in one LIMIC – Cameroon (Gottesfeld et al., 2013) .  HICs are likely to have safe systems of work in place having evidenced the potential dangers over many decades. 1 4 4 HIC  Workers in LIMICs are likely to have less stringent safe systems of work and less access to PP E to protect them from Pb exposure. 3 4 12 LIMIC Multiple substances Open burning of CDW Construction and demolition workers NGA, global, USA  Several papers evidence d that open burning is used to dispose of CDW (Nie et al., 2015; Ogunmakinde et al., 2019; Wahab and Lawal, 2011) or that it is used as fuel (Dania et al., 2007)  Risk of dioxin production is high, particularly from the combustion of PVC but also from wood sources (Carroll, 2001; Kodros et al., 2016; Lemieux et al., 2004; Wiedinmyer et al., 2014) .  Emissions from CCA treated wood characterised (Wasson et al., 2005) , noting that DRC formation was limited but levels of Cr, Cu, and As were very high.  The data for CDW specifically are limited and more work is needed in this area.  Both formal and informal workers operate without respiratory protec tive equipment. 4 4 16 LIMIC Population  Adults and children are unable to avoid exposure if they live around e - waste open burning activities. 4 4 16 Abbreviations: Likelihood (L); severity (S); risk (R); low income and middle income countries (LIMIC); high income countries (HIC); hydrogen sulphide (H 2S); persistent organic pollutants (POP); construction and demolition waste (CDW); dioxins and related compounds (DRC); chromated copper arsenate (CCA); polyvinyl chloride (PVC); personal protective eq uipment (PPE). 63 6. Conclusions As we have shown in this systematic review, some construction and demolition processes result in the transformation and physical movement of materials and substances in CDW, thus creating pathways through whic h human can be e xposed to harm to approximately 200 million formal and informal workers worldwide (Mella and Savage, 2018) . Data to indicate how man y of those work with waste is not available , and speculatively may never become so due to the lack of prioritisation for this metric . Yet many of the CDW related high risk hazard -pathway -receptor comb inations identified here involve the aerosolisation of particles and substances, or involve accidents, all of which affect the entire construction and demolition workforce , regardless of their direct or specialist involvement with waste . Asbestos, a long standing, potentially lethal , and prolific material, continues to cause the occupational d eaths of approximately 90,000 -250,000 people every year. Although t he majo rity of these occur in HICs where historical use of the material has been concentrated, the use of asbestos in LIMICs has continued in the last several decades ; chrysotile has yet to be banned in 39 countries that consumed 1.1 Mt in 2017. Whereas Russia pr oduces just over half of it, India and China consume approximately half, and India’s apparent ignorance of the potential hazards means that almost half of the 1.25 million deaths anticipated from asbestos in the coming years are expected to occur on the su bcontinent . The substantial stocks of asbestos that exist throughout the global built environment mean that exposure to asbestos will continue to be a significant cause of death and ill -health over the coming decades, as engineered structures reach their end of life, often demolished by unprotected and untrained informal workers across LIMICs. There is a surprising lack of data to indicate the number of injuries and fatalities specifically on demolition sites, given that these workplaces are intuitively high-risk, especially for informal workers in LIMICs . Acknowledging this lack of evidence, we have tentatively assigned and highlighted a medium to high level of risk of physical injury for demolition workers in LIMICs with a recommendation that the strengt h of knowledge is considerably improved in these contexts. A similar lack of dat a exists to evidence the scale of open burning that takes place on construction and demolition sites across the world. Whereas only a small proportion (wt.) of 64 CDW material s are combustible, several substances of concern may be released in open, uncontrolled fires that is thought to be used as a common method of disposal in countries where MSW mismanagement is reported to be high. Given the prevalence of PVC in CDW the hazards a ssociated with exposure to DRCs from open burning may be as yet, an increasing cause for concern. However , until the activity prevalence can be determined, it is challenging to assess the magnitude of these emissions , and hence , potential harm to human health. The general quality of studies reviewed here was mixed, ranging from several complex and ambitious global burden of disease studies on asbestos through to insufficiently methodologically documented studies in LIMICs ; some of these case studies which lacked sufficient context to be generalisable across wid er socio -economic conditions . This lack of robust research into solid waste and human health in countries where ri sks are likely to be higher, can be expected to encourage the continuation of elevated risk practices . Given the very large number of workers in volved in the construction sector, the high level of informality, and the very large quantities of waste involved, it is strongly recommended that further research into CDW in LIMICs is carried out to address an d mitigate the level of potential harm cause d by the mismanagement of these materials. 65 CRediT author statement Ed Cook: Conceptualization; Data curation; Formal Analysis; Investigation; Methodology; Project administration; Resources; Validation; Visualization; Writing – original draft; Writing – review & editing. Costas A. Velis: Conceptualization; Data curation; Formal Analysis; Funding acquisition; Investigation; Methodology; Project administration; Resources; Software; Supervision; Validation; Visualization; Writing – original draft; Writing – review & editing. Acknowledgements We are grateful to the Technical Advisory Board of the Engineering X Safer End of Engineered Life programme , of the Royal Academy of Engineering for their steering and insightful feedback, especially on early versions of this research and manuscript. The Programme Board chaired by Professor William Powrie & the Academy staff , especially Hazel Ingham and Shaarad Sharma who provided support throughout the process. Ad hoc advice, guidance and criticism was provided by mult iple stakeholder representatives, as listed in the relevant Academy report . We are grateful Nick Rigas (D -Waste), for the presentation of infographics and to Dr Godwin Akpeimeh for preliminary data collection . The research communicated and opinions expressed here are authors’ alone. Financial We gratefully ac knowledge funding from the Royal Academy of Engineering. This work was commissioned as part of the Engineering X Safer End of Engineered Life programme which is funded by Lloyd’s Register Foundation. Engineering X is an international collaboration, founded by the Royal Academy of Engineering and Lloyd’s Register Foundation, that brings together some of the world’s leading problem -solvers to address the great challenges of our age. 66