ENVIRONMENTAL AND OCCUPATIONAL HEALTH RISKS OF RECYCLED MATERIALS IN ASPHALT PRODUCTION

Project leader: Asko Saarela, Technical Research Centre of Finland (VTT), Building and Transport, P.O.Box 1805, FIN-02044 VTT, Finland, tel. +358-9-456 4970, e-mail: Asko.Saarela@vtt.fi
 
 

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TIIVISTELMÄ SUOMEKSI

Researchers:
Dr. Pirjo Heikkilä, Finnish Institute of Occupational Health (FIOH), Department of Epidemiology and biostatistics, Topeliuksenkatu 41 aA, 00250 Helsinki, tel. +358-9-4747215, e-mail: Pirjo.Heikkila@occuphealth.fi
M.Sc Mervi Hämeilä, FIOH, Department of Industrial Hygiene and Toxicology, tel. +358-9-4747484,  e-mail: Mervi.Hameila@occuphealth.fi
M.Sc Virpi Väänänen, FIOH, Department of Industrial Hygiene and Toxicology, tel. +358-9-4747809,  e-mail: Virpi.Vaananen@occuphealth.fi
Dos. Kaija Linnainmaa-Jaakkola, FIOH, Department of Industrial Hygiene and Toxicology, tel. +358-9-4747809, e-mail: Kaija.Linnainmaa@occuphealth.fi
Dr Petri Peltonen, VTT Building and transport, Environmental Engineering, P.O.Box 1804, 02044 VTT, tel. +358-9-456 4987, e-mail: Petri.Peltonen@vtt.fi
Dr Pentti Kalliokoski, University of Kuopio, Faculty of Environmental Sciences, P.O.Box 1627, 70211 Kuopio, tel. +358-9-17-162 211, e-mail: Pentti.Kalliokoski@uku.fi
M.Sc. Jukka-Pekka Kasanen, University of Kuopio, Faculty of Environmental Sciences, P.O.Box 1627, 70211 Kuopio, tel. +358-9-17-163 220, e-mail: Jukkapekka.Kasanen@uku.fi

Financing SYTTY organisation: The Academy of  Finland
Funding from SYTTY / Total funding of project (€): 111306 / 314699
Person-months of work funded by SYTTY / Total person-months of work: 33,5 / 74,9

KEY WORDS: asphalt, occupational, wastes, recycling, fumes
 

EXTENTED ABSTRACT

1 Introduction

The utilisation of waste is under continuous study in Europe. The goal of EU's waste management is to decrease the  formation of waste and to increase the recycling and utilisation of wastes, primarily as materials for reuse, and secondly as a source of energy. There are increasing efforts to use waste materials, e.g. in road construction. Pilot studies on some recycled materials such as cellulose fibres, waste plastic, hematite, and coal fly ash have shown that technically these products can be used in road paving. The environmental and occupational health risks in the use of these products in asphalts are not known however.

The aim of  the project was to study the composition of bitumen emissions in laboratory and field conditions, the exposure of asphalt workers, health effects, and dissolution of hazardous components into the environment when organic and inorganic, recycled industrial by-products were used in asphalt mixes. The project started in 1998 and will continue until the end of 2002. The project was suspended for a year due to the maternity leave of the project worker.

2 Methods

Methods for diffusion testing
Diffusion testing reveals the acceptable environmental water solubility of solid materials. The testing was based on the Dutch diffusion test (NEN 7343) in which leaching of inorganic impurities from solid materials, e.g. coal fly ash in the asphalt concrete, can be measured. In the test, the compacted asphalt concrete sample or the core sample was stored for 64 days in acidified water. The results were compared with the environmental water solubility limits of the test.

Assessment of occupational health risks
Generation of fumes in the laboratory
Fumes from bitumen, bitumen modified with waste plastic, with tall oil pitch, bitumen containing lime stone or coal flash were generated by heating the bitumen and the bitumen mixes in a glass vessel to temperatures used in road paving. The amount of the waste materials in the mixes was 10 w-% .

Field studies
The occupational exposure of the workers was surveyed during the laying of the following mixtures at altogether nine paving sites during the paving seasons in 1999-2000 :
- stone mastic asphalt (SMA) containing coal fly ash as a filler (paving temp. 170-180°C)
- SMA containing lime as a filler (paving temp. 170-180°C)
- remixing (REM) of SMA containing coal fly ash (heating with liquefied gas, heating temp. above 200°C)
- remixing of SMA containing lime (heating with liquefied gas, heating temp. above 200°C)
- remixing of asphalt concrete (heating with fuel oil, heating temp. above 200°C)

The effects of coal fly ash in the work environment were evaluated by measuring the inhalation and dermal exposures of asphalt workers: paver operator, heating machine operator in REM, screedman, shoveller, roller driver, and traffic controller. The exposure to polycyclic aromatic compounds was also monitored by analysing the concentration of the metabolites of naphthalene, phenanthrene and pyrene in the urine samples of the paving workers.

The concentrations of the following air impurities were monitored: inhalable dust, bitumen fumes, bitumen vapours, vaporous and particulate polycyclic aromatic hydrocarbon (PAH) compounds.

The methods used in the monitoring of exposure were:
- inhalable dust: teflon filters, gravimetry
- bitumen fumes: teflon filters, Fourier Transform Infrared Spectroscopy (FTIR)
- bitumen vapours: XAD-2 –tubes, gas chromatography (GC)
- vaporous and particulate PAHs: high pressure liquid chromatography (HPLC)
- carbon monoxide, nitrogen and sulfur oxides
- metabolites in urine samples: HPLC and GC
- survey of experienced symptoms by a questionnaire.
- dermal exposure to PAHs: hand washing with sun flower oil and wiping with Kleenex tissues.

Testing of genotoxicity
Mutagenicity was investigated by the Ames Salmonella bacteria assay. Five concentrations of each DMSO extract were tested using frameshift mutation strains TA98 (various frameshift mutagens) and YG1024 (sensitive to aromatic nitro-, amino and hydroxyamino compounds). The tests were performed by standard protocols according to the OECD guidelines. Both vaporous and particulate fractions generated in the laboratory were tested with and without metabolic activation (S9-mix). Because of the negative testing results with the vapour fractions generated in the laboratory, only particulate fractions of the field samples were studied.

Testing of sensory irritancy
The standard mouse bioassay will be used for obtaining the RD50 (i.e., the concentration that causes a 50% decrease in respiratory frequency) and for estimating the irritation properties of bitumen fumes  and fumes from a mix containing waste plastic. The effects of fumes on the respiratory rate, tidal volume, expiratory flow rate, time of inspiration, time of expiration, and respiratory patterns will be monitored by the Alarie-test in 2002.

3 Results and discussion

Diffusion
Composition of fumes generated in the laboratory
The main components in the fumes and vapours from modified bitumens were the same as those from bitumen. These components were n-alkanes (fumes: C10H22-C29H60 and vapours: C8H18-C19H40), branched hydrocarbons alkyl benzenes. The main alkyl benzenes were xylene, toluene and also styrene in the case of the waste plastic bitumen. All fumes and vapours contained organic sulfur compounds, such as benzothiophenes and dibenzothiophenes. The main components of PAHs were alkyl naphthalenes, phenanthrenes, fluorenes and pyrenes.

The concentration of aldehydes ( acetaldehyde-aldehyde, propionaldehyde-aldehyde and benzoaldehydes) was highest in the emissions of the bitumen containing tall oil pitch. Formaldehyde, which is the most irritant aldehyde, was not detected in these emissions. Chlorophenols and polychlorinated benzenes as well as traces of the polychlorinated biphenyls were detected in the emissions from bitumens containing waste plastics.

Genotoxicity
The fumes from bitumen modified with waste plastics gave rise to mutations without metabolic activation. A clear dose-response was observed with both strains used: TA98 and YG1024. Bitumen fumes and the fumes of bitumen modified with coal fly ash were negative in the tests without metabolic activation, but were weakly mutagenic with a dose-response in the strain TA98 in the presence of metabolic activation.

All the fume samples collected from the remixing sites were mutagenic with the strain TA98 in the presence of metabolic activation. The use of coal fly ash instead of lime as a filler in the asphalt did not potentiate the mutagenicity of the fumes. The high heating temperature applied in the remixing of old asphalts increased the mutagenicity of the fumes considerably.

Occupational exposures
The measured concentrations of bitumen fume, total PAHs (15 identified PAH compounds), PAHs with 4-6 aromatic rings (carcinogenic PAHs) and 1-pyrenol in the urine of the paving workers in 1999 - 2000 are presented in Figures 1-4.

4 Conclusions

The results of the exposure measurements show that the use of inorganic recycled material, coal fly ash, did not affect the concentrations of the exposure indices: bitumen fume, vaporous and particulate PAHs, and metabolites of PAHs in urine. The laying temperature and weather conditions influenced the air concentrations of the bitumen fumes and PAHs more than did the use of coal fly ash. The results are in accordance with the general knowledge that inorganic materials that do not contain hazardous impurities in significant amounts, do not evaporate at paving temperatures.

The results of the laboratory studies show that the main components in the fumes from both bitumen and bitumen containing waste plastics were identical, but that additionally, the emissions from waste plastics contained small amounts of chlorinated phenols, benzenes and biphenyls. The use of waste plastics in bitumen increased the mutagenicity of the fumes in the laboratory tests.

The use of coal fly ash instead of lime as a filler in asphalt did not affect the exposure of the paving workers nor the mutagenicity of the fumes. Thus inorganic fillers, such as coal fly ash, that do not contain hazardous impurities in significant amounts, are applicable for asphalt mixes. The use of organic additives, e.g. waste plastics, may alter the health effects of air impurities emitted from the asphalt mixes. However, more data are needed to assess the suitability of organic additives.

High paving or heating temperatures increased the exposure and the mutagenicity of the fumes. Controlling the paving and remixing temperatures is therefore highly recommended.

Fig. 1. Bitumen fume concentrations presented as averages (.), result levels (-) in % and ranges (*) as max. and min. values at breathing zone of workers in laying and remixing of SMA containing lime or coal fly ash (CFA) as a filler.

Fig. 2. Total PAH concentrations (averages and ranges) at breathing zone of workers in laying and remixing of SMA containing lime or coal fly ash (CFA) as a filler

Fig. 3. Concentrations (averages and ranges) of 4-6 ring PAHs at breathing zone of workers in laying and remixing of SMA containing lime or coal fly ash as a filler.

Fig.4. 1-Pyrenol concentrations (averages and ranges) in urine samples collected at the end of shift of workers in laying and remixing of SMA containing lime or coal fly ash and in urine of traffic controllers.
 
 

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