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Aldehydes in the atmospheric environment: evaluation of human exposure in the north-west area of Milan
Microchemical Journal 67 Ž2000. 11᎐19
Aldehydes in the atmospheric environment: evaluation of human exposure in the north-west area of Milan Bianca Patrizia Andreini, Roberto Baroni, Elisa Galimberti, Giulio SesanaU U.O. Chimica, Presidio Multizonale di Igiene e Pre¨ enzione, ASL Pro¨ incia di Milano n.1, Via Spagliardi, 19, 20015 Parabiago, Milan, Italy
Abstract Human exposure to aldehydes has been evaluated in five urban locations and one rural-industrial location in the north-west area of Milan in winter 1999 and in summer 1998᎐99. Ambient air samples collected on dinitrophenylhydrazine ŽDNPH.-coated diffusive cartridges were analysed for aldehydes as their DNPH-derivatives. Aldehydes have been identified and their concentration measured via HPLC-UV and LC-APCI-MS negative ion mode methods. During the winter the range of total concentration of aldehydes was 16.7᎐30.7 grm3 at the urban locations and 11.7 grm3 at the rural-industrial location. Formaldehyde accounted for 50% of the total amount of carbonyl compounds in all locations; the percentage of acetaldehyde was more variable: 23᎐38% of the total carbonyls. The contribution of outdoor environment to the average human daily intake of formaldehyde in this area Žurban and rural-industrial . is mostly 1᎐2% of the total human exposure. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Aldehydes; Air concentration; HPLC; LC-APCI-MS; Toxicological aspects
1. Introduction Carbonyl compounds are of critical importance in atmospheric chemistry, since they are stable intermediate products of the photochemical oxidation of virtually all hydrocarbons and precursors to free radicals, ozone and peroxyacyl nitrates w1,2x. Several carbonyls are important be-
U
Corresponding author.
cause of their irritant and toxic properties, mutagenicity and carcinogenicity: formaldehyde w3x and acetaldehyde w4x have received regulatory attention and are currently monitored in the north-west area of Milan where the ambient air quality standards for micropollutants are evaluated. In this paper we describe the results of a study in which ambient levels of aldehydes have been measured at five urban locations and at a ruralindustrial location in summer and in winter using diffusive sampling. This study of ambient car-
0026-265Xr00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 6 - 2 6 5 X Ž 0 0 . 0 0 0 8 7 - 4
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B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
bonyls has been carried out as part of a larger effort whose aim was the monitoring of human exposure to organic air pollutants. The aldehydes measured in this study are in the range C 1 ᎐C 8 , identified using a HPLC method with gradient elution and UV detection and a LC-APCI-MS method. The relative variations of the concentrations of aldehydes and of other measured pollutants during the studied periods were investigated. The contribution of outdoor environment to the average human daily intake of formaldehyde has been evaluated.
2. Materials and methods 2.1. Sampling strategy Ambient air samples were collected on 11᎐18 January 1999 at five urban locations in the northwest area of Milan wLegnano ŽSavonarola, Town Hall., Bollate ŽRosselli, Town Hall., Parabiago ŽSpagliardi.x. In Parabiago air samples were also collected in June and July 1999. Air samples from the rural-industrial area ŽBoffalora. were collected in August 1998 and in January 1999. At each site the sampling duration was 24 or 72 h Ž24 h from Monday to Thursday and 72 h from Friday to Sunday. if not otherwise specified. 2.2. Materials All solvents employed were HPLC-grade. The carbonyl 2,4-dinitrophenylhydrazine ŽDNPH. derivatives and the calibration standard ŽCarbonyl-DNPH Mix 1. containing 13 components ŽDNPH derivatives of acetaldehyde, acetone, acrolein, benzaldehyde, 2-butanone, nbutyraldehyde, crotonaldehyde, formaldehyde, hexanaldehyde, methacrolein, propionaldehyde, p-tolualdehyde, valeraldehyde. were purchased from Supelco. 2.3. Sampling system and analytical procedure The diffusive sampling cartridges Radiello purchased from Fondazione S. Maugeri ŽPadova.
were made of a 100᎐mesh s.s. net cylindrical chemi-adsorbing cartridge, o.d. 5.9 mm, containing 900 mg of 35᎐50 mesh 2,4-dinitrophenylhydrazine coated fluorisil. Following sample collection, the cartridges were eluted with 2 ml of acetonitrile. The acetonitrile extracts were analysed by liquid chromatography as described below. Aldehydes were identified in 57 air samples. 2.3.1. HPLC-UV analysis Each acetonitrile solution of carbonyl-DNPH standards and of air samples were analysed by liquid chromatography ŽLC. with UV detection ŽHewlett Packard Model 1050.. The column used was a 5-m C 18 Hypersil ŽHP. Ž250 mm length = 4.6 i.d... Separations were carried out at 25⬚C using the following mobile-phase gradient: flow rate, 1 mlrmin; 60% solvent A, 30% solvent B and 10% solvent C for 15 min Žsolvent A, water; solvent B, acetonitrile; solvent C, THF.; from 60 to 30% solvent A, 10% solvent C constant, within 25 min; then 5 min isocratic. The detection wavelength was 360 nm. The absorbance at the given wavelength Žpeak height or peak area. of five standard mixtures of DNPH-derivatives of aldehydes were used to construct the external calibration curves employed to measure the concentration of DNPH-derivatives of aldehydes in the ambient air samples. The concentrations of DNPH-derivatives of aldehydes in blank cartridges were measured. Analyses of blank cartridges yielded a quantity of formaldehyde lower than 0.1 g and of other aldehydes lower than 0.001 g. Blank correction was carried out for each analytical batch. Analytical precision was 1.5᎐2.5% at the 0.50 grml level. The limit of detection was 0.5 ng. 2.3.2. LC-APCI-MS analysis 2.3.2.1. Equipment. Hewlett Packard series 1100 MSD liquid chromatograph ŽPalo Alto, CA, USA. with a Quaternary Pump, an injector with a 20 l loop and APCI-MS detection. The column used was a 5-m C 18 Hypersil ŽHP. Ž250 mm length = 4.6 i.d... Separations were carried out at 25⬚C using the following binary mobile-phase gradient:
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
flow rate, 1 mlrmin; 50% solvent A, 50% solvent B for 10 min Žsolvent A, water; solvent B, acetonitrile.; from 50 to 30% solvent A, within 25 min; from 30 to 20% solvent A, within 10 min, then 5 min isocratic. 2.3.2.2. Optimization of LC-APCI-MS. The working conditions for the APCI were the following: drying nitrogen heated to 350⬚C and injected in the capillary region at a flow rate of 4 lrmin; the corona current was 25 A and the capillary voltage was 4000 V. An APCI negative ion mode ŽNI. was used and full scan data acquisition was performed scanning from m r z 90 to 500 to obtain the molecular ions wM-Hxy for each compound ŽTable 1.. The identification of DNPH-derivative of aldehydes in environmental samples was carried out using selected ion monitoring-negative ion acquisition mode ŽSIM-NI. in order to obtain lower detection limits. Table 1 summarizes the wM-Hxmasses of DNPH-derivatives of carbonyls identified.
3. Results and discussion 3.1. Diffusi¨ e sampling and HPLC-UVr LC-APCIMS analysis of ambient air samples The aim of this study was the evaluation of the Table 1 Molecular mass series of DNPH-Carbonyl derivatives DNPH derivative of:
MW
Molecular ion wM-Hxy
Formaldehyde Acetaldehyde Acetone Acrolein Propanal Crotonaldehyde Methacrolein 2-Butanone n-Butanal Benzaldehyde n-Pentanal m-Tolualdehyde n-Hexanal
210 224 238 236 238 250 250 252 252 286 266 300 280
209 223 237 235 237 249 249 251 251 285 265 299 279
13
extent of 24᎐72 h average human exposure to aldehydes by inhalation route. Therefore, diffusive sampling was preferred to pumped sampling in order to estimate the levels of carbonyl compounds in air. Moreover the overall uncertainty Žsampling q analysis . of diffusive samplers is reported to be slightly lower than that obtained with pumped sampling w5x. All ambient air samples contained many carbonyls. The HPLC-UV method allowed the separation of all the components of the standard mixture employed to build the calibration curve. However, during this study our interest was devoted to measure the concentration of the following aldehydes: formaldehyde, acetaldehyde, propanal, crotonaldehyde, n-butanal, n-pentanal, benzaldehyde, m-tolualdehyde, hexanal. Acrolein was identified in the air samples, however, the concentrations are not reported in this study, because sampling of acrolein on DNPH cartridge is usually reported to underestimate the true value w5x. The APCI in the negative ion mode generated mass spectra with only the wM-Hxy ion present in the operative conditions used. This technique gave independent confirmation of carbonyl structure for the aldehydes identified via HPLC-UV. In the chromatographic method employed in the LCAPCI-MS acetone and acrolein coeluted, however, they were easily identified from the different molecular ions ŽFig. 1.. LC-APCI-MS allowed the identification of carbonyl compounds in air extracts not easily revealed via HPLC-UV w6,7x. Many LC-MS chromatograms of air samples showed a signal between the signals of acetaldehyde and acetoneracrolein, whose APCI spectrum showed a wM-Hxy ion of m r z 363 as reported by other authors. It has been suggested to be a ‘reaction product between 2,4-dinitrophenylhydrazone and 2,4-dinitrochlorobenzene’ produced on-cartridge in the presence on nitrogen dioxide and HCl w7x. 3.2. Winter samplings During the week 11᎐18 January 1999 the sampling of ambient air samples and the measurements of the concentration of aldehydes were performed in five urban locations ŽLegnanor
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
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Fig. 1. HPLC-MS base peak chromatogram obtained by APCI-SIM-NI of the standard mixture of DNPH carbonyls. Table 2 Average carbonyl concentrations on 11᎐18 January 1999 Urban
Formaldehyde Acetaldehyde Propanal Crotonaldehyde n-Butanal Benzaldehyde n-Pentanal m-Tolualdehyde Hexanal Total aldehydes
BollateRosselli Žgrm3 .
Bollate Town Hall Žgrm3 .
Legnano Savonarola Žgrm3 .
Legnano Town Hall Žgrm3 .
Parabiago Žgrm3 .
Rural-industrial Boffalora Žgrm3 .
8.0 Ž"0.8. 5.1 Ž"2. 0.7 Ž"0.5. - 0.5 - 0.5 - 0.5 - 0.5 2.2 Ž"0.9. - 0.5 16.7 Ž"3.4.
9.8 Ž"1.8. 6.8 Ž"0.9. 1.2 Ž"0.2. - 0.5 - 0.5 0.5 Ž"0.5. - 0.5 - 0.5 - 0.5 19.0 Ž"3.7.
9.5 Ž"1.9. 6.5 Ž"1.2. 1.3 Ž"0.2. - 0.5 0.5 Ž"0.5. - 0.5 1.1 Ž"1.1. 2.3 Ž"0.7. - 0.5 25.2 Ž"4.1.
15.7 Ž"17.5. 7.3 Ž"8.4. 1.6 Ž"1.9. - 0.5 0.8 Ž"1.7. 1.6 Ž"2.1. - 0.5 3.1 Ž"2.8. - 0.5 30.7 Ž"35.5.
9.5 Ž"3.1. 6.1 Ž"1.6. 2.4 Ž"2.5. - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 17.9 Ž"4.8.
5.9 Ž"1.3. 4.5 Ž"1.3. 0.6 Ž"0.6. - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 11.7 Ž"2.9.
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
Savonarola and Town Hall, BollaterRosselli and Town Hall, ParabiagorSpagliardi. and in a ruralindustrial location ŽBoffalora.. Formaldehyde, acetaldehyde and propanal were present in almost
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all samples, however, crotonaldehyde was always absent. The average values and standard deviations of the concentrations of all aldehydes measured in
Fig. 2. Ambient concentrations of Žfrom top to bottom. formaldehyde, acetaldehyde, propanal, m-tolualdehyde at Žfrom left to right. Bollate-Rosselli, Bollate-Town Hall, Legnano-Savonarola, Legnano-Town Hall, 11᎐18 January 1999. ŽSampling of 15 January is a 72-h one..
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B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
the winter week are listed in Table 2. Ambient concentrations of four of the carbonyls studied here are shown in time series in Fig. 2: formaldehyde, acetaldehyde, propanal and m-tolualdehyde Žpentanal and benzaldehyde were seldom present.. m-Tolualdehyde is not shown in Fig. 3. The temporal variation of formaldehyde and of acetaldehyde in each location is very similar. Moreover, the same temporal variation of aldehydes is present in four out of six locations. Usually a maximum is present on 14 January ŽThursday. and a minimum is present in the 72 h sampling Ž15᎐18 January.. The variation of concentration of all aldehydes in Legnano is slightly different from the other locations, in particular Legnano Town Hall, which presented a severe episode of smog pollution on 12 January. In fact, high concentrations of several other pollutants were found on that day Žbenzene, toluene, particulate, benzow axpyrene.. Formaldehyde was the most abundant aldehyde in all samples and accounted for 50% of the total aldehydes concentrations measured in most samples. Ambient levels of formaldehyde ranged from 4.1 to 53.4 grm3 at the six locations. The week average values ranged from 8.0 to 15.7 grm3 at the five urban locations; the average value in the
rural-industrial location was 11.7 grm3. Acetaldehyde concentrations ranged from 2.1 to 25.7 grm3 , the rural-industrial location presenting the lowest average value. Acetaldehyde accounted for 25᎐45% of the total ambient aldehydes concentration at the urban locations. The higher molecular weight carbonyls accounted for a modest fraction of total aldehydes. The meteorological conditions Žtemperature, wind speed, duration and amount of rainfall . had a strong influence on concentrations of all pollutants: as expected, windy and rainy days Ž11 January. presented the lowest concentrations of pollutants, on the other hand sunny days, low wind speed and stable atmospheric conditions induced an increase of the concentration of aldehydes during the week until 14 January. Fig. 4 shows the different variation of total measured aldehydes with respect to meteorological conditions in the rural and in the urban areas. In the latter primary emissions from mobile sources had a strong influence on the levels of aldehydes even in rainy days. This effect is probably related to a limited scavenging effect in the urban area. A typical reduction of total carbonyl concentrations Žsee Fig. 4. in all locations Žexcept at Bollate-Rosselli. is present during the week-end,
Fig. 3. Ambient concentrations of Žfrom top to bottom. formaldehyde, acetaldehyde, propanal, m-tolualdehyde at Parabiago and Boffalora, 11᎐18 January 1999.
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
confirming traffic as a major source of emissions in the north-west area of Milan. Moreover, the entity of reduction is different in the six locations according to the local traffic situation. 3.3. Summer sampling Sampling of carbonyls was performed in the rural-industrial location for three weeks in summer 1998 Ž16 July᎐6 August. and in the urban location, Parabiago-Spagliardi, for 2 weeks in 1999 Ž12᎐23 July, 23᎐30 August.. Ambient concentrations of four of the carbonyls studied in 1998 are shown in time series in Fig. 5a. The temporal variation of formaldehyde and acetaldehyde at Boffalora in 1999 is reported in Fig. 5b. The average values and standard deviations of the concentrations of all aldehydes measured in the two locations are listed in Table 3. Ambient levels of formaldehyde accounted for 16᎐92% of total aldehydes concentration in Boffalora, for 30᎐46% in Parabiago; they ranged from 4.6 to 15.9 grm3 in Boffalora, average value being 7.5 grm3, and from 6 to 12.5 grm3 in Parabiago, average level being 8.6 grm3. Acetaldehyde accounted for 7᎐42% in Boffalora Žrange: 1.3᎐6.7 grm3 , average: 4.5 grm3 . and 42᎐62% in Parabiago Žrange: 6.4᎐25 grm3 , average: 12.8 grm3 .. Meteorological conditions and week-end reduction of traffic strongly influence the summer concentrations of aldehydes as already observed in winter measurements. In fact lower concentra-
17
tions of carbonyls were observed in rainy and windy days such as 27 and 28 July in comparison with the high values observed in the sunny days of the previous week in Boffalora. The week-end reduction of aldehyde levels is strongly evident in the two sunny weeks in Parabiago. At Boffalora all the aldehydes investigated were present in several samplings; n-butanal, n-pentanal and hexanal, absent in the winter sampling were randomly present in summer, therefore, the total aldehyde concentration is usually higher in summer than in winter. However, season does not seem to strongly affect average values of formaldehyde and acetaldehyde in Boffalora ŽStudent’s t-test: Ps 0.209.. Parabiago seems more affected by seasonal differences, in particular acetaldehyde concentrations are higher in summer than in winter. In relation to the observed data the contribution of photochemical production to aldehydes levels resulted more evident during summer months. In all locations benzene, toluene, ethylbenzene and xilene ŽBTEX. were measured in ambient samplings in parallel to aldehyde samplings. The temporal variation of total BTEX concentration was very similar to that of formaldehyde, as described in Fig. 6 ŽBoffalora in 1998.. This variation is typical of all locations and of each period. 3.4. Toxicological e¨ aluation The collected data are a starting point to evalu-
Fig. 4. Daily total measured aldehydes at Bollate-Rosselli, Bollate-Town Hall, Legnano-Savonarola, Legnano-Town Hall, Parabiago and Boffalora, 11᎐18 January 1999. Note meteorological situations on x-axis.
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
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Table 3 Average carbonyl concentrations in Boffalora, summer 1998 and Parabiago, summer 1999
Formaldehyde Acetaldehyde Propanal Crotonaldehyde n-Butanal Benzaldehyde n-pentanal m-Tolualdehyde Hexanal Total aldehydes
Urban Parabiago Žgrm3 .
Rural-industrial Boffalora Žgrm3 .
8.9 Ž"1.9. 13.7 Ž"5.7. 1.1 Ž"0.2. - 0.5 1.1 Ž"0.4. - 0.5 - 0.5 - 0.5 - 0.5 24.8 Ž7.9.
7.5 Ž"2.7. 4.5 Ž"1.7. 2.0 Ž"2.8. - 0.5 1.2 Ž"1.5. - 0.5 - 0.5 - 0.5 - 0.5 15.8 Ž"6.2.
ate the risk associated to outdoor exposure to aldehydes for people living in the investigated area. Table 2 and Table 3 summarize the average concentrations of aldehydes in a typical winter week presenting different atmospheric events and in a summer period typical of Pianura Padana, high temperature and humidity, low wind speed and sporadic rain. The levels of formaldehyde in the rural-industrial location are typical of areas not directly
interested by specific emissions and are mostly due to traffic emissions, as the urban levels in winter and in summer. The concentrations of all aldehydes during the week-end could be considered the base level of human exposure in winter and in summer. Formaldehyde is ubiquitous: indoor levels are reported to range from 10 to 4000 grm3 ; the contribution of various atmospheric environments to the average human daily intake has been calculated to be 0.02 mgrday for outdoor air in the investigated area and for similar areas 3. Therefore, outdoor exposure in the north-west area of Milan is a minimal fraction of total human exposure. The toxicological approach suggests that the levels of formaldehyde found in this area should not cause any acute toxic effect and any chronic effect, however, epidemiological studies need to be performed to support this hypothesis. Levels of acetaldehyde are usually lower than 10 grm3, except for the urban location in summer. These levels should not cause irritant effect or acute or chronic effects. In fact on the basis of data on irritancy in humans, a tolerable concentration of 2 mgrm3 has been derived; however, with respect to the induction of tu-
Fig. 5. Daily values for aldehydes observed at Ža. Boffalora in summer 1998 and Žb. Parabiago in summer 1999.
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
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Fig. 6. Variation with time of total aldehydesŽleft. and total aromatic compounds Žright. at Boffalora in summer 1998.
mours, the concentrations associated with a 10 5 excess lifetime risk are 11᎐65 grm3 w8x.
4. Conclusions The HPLC-UV and LC-APCI-MS negative ion mode methods were employed to evaluate the presence of aldehydes in ambient air samples. By-products were identified in the samples through the APCI-NI method. The concentration of aldehydes in the north-west area of Milan were higher in the urban locations with respect to the rural-industrial one. Concentrations were slightly higher in summer than in winter. The measured levels of formaldehyde and acetaldehyde suggested that outdoor exposure is a minimal fraction of the daily human exposure. These levels should not cause any acute or chronic toxic effect on humans on the basis of a toxicological approach. However, an epidemiological study needs
to be performed in that area to evaluate the contribution of low concentrations of aldehydes in presence of other micropollutants such as aromatic compounds, ozone and nitrogen oxides. References w1x A. Vairavamurthy, J.M. Roberts, L. Newman, Atmos. Environ. A 26 Ž1992. 1965. w2x P.D. Lighfoot, R.A. Cox, J.N. Cowley et al., Atmos. Environ A 25 Ž10. Ž1992. 1805. w3x Formaldehyde, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 62, IARC, Lyon, 1995 and references therein. w4x Acetaldehyde, IARC Monographs on the evaluation of carcinogenic risks to humans, vol. 36, IARC, Lyon, 1985 and references therein. w5x E. Goelen, M. Lambrechts, F. Geyskens, Analyst 122 Ž1997. 411. w6x E. Grosjean, D. Grosjean, M.P. Fraser, G.R. Cass, Environ. Sci. Technol. 30 Ž1996. 2687. w7x S. Kolliker, M. Oehme, C. Dye, Anal. Chem. 70 Ž1998. 1979. w8x WHO, Acetaldehyde Environmental Health Criteria Vol. 167. Geneva. IPCS Ž1995. and references therein.
Aldehydes in the atmospheric environment: evaluation of human exposure in the north-west area of Milan Bianca Patrizia Andreini, Roberto Baroni, Elisa Galimberti, Giulio SesanaU U.O. Chimica, Presidio Multizonale di Igiene e Pre¨ enzione, ASL Pro¨ incia di Milano n.1, Via Spagliardi, 19, 20015 Parabiago, Milan, Italy
Abstract Human exposure to aldehydes has been evaluated in five urban locations and one rural-industrial location in the north-west area of Milan in winter 1999 and in summer 1998᎐99. Ambient air samples collected on dinitrophenylhydrazine ŽDNPH.-coated diffusive cartridges were analysed for aldehydes as their DNPH-derivatives. Aldehydes have been identified and their concentration measured via HPLC-UV and LC-APCI-MS negative ion mode methods. During the winter the range of total concentration of aldehydes was 16.7᎐30.7 grm3 at the urban locations and 11.7 grm3 at the rural-industrial location. Formaldehyde accounted for 50% of the total amount of carbonyl compounds in all locations; the percentage of acetaldehyde was more variable: 23᎐38% of the total carbonyls. The contribution of outdoor environment to the average human daily intake of formaldehyde in this area Žurban and rural-industrial . is mostly 1᎐2% of the total human exposure. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Aldehydes; Air concentration; HPLC; LC-APCI-MS; Toxicological aspects
1. Introduction Carbonyl compounds are of critical importance in atmospheric chemistry, since they are stable intermediate products of the photochemical oxidation of virtually all hydrocarbons and precursors to free radicals, ozone and peroxyacyl nitrates w1,2x. Several carbonyls are important be-
U
Corresponding author.
cause of their irritant and toxic properties, mutagenicity and carcinogenicity: formaldehyde w3x and acetaldehyde w4x have received regulatory attention and are currently monitored in the north-west area of Milan where the ambient air quality standards for micropollutants are evaluated. In this paper we describe the results of a study in which ambient levels of aldehydes have been measured at five urban locations and at a ruralindustrial location in summer and in winter using diffusive sampling. This study of ambient car-
0026-265Xr00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 6 - 2 6 5 X Ž 0 0 . 0 0 0 8 7 - 4
12
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
bonyls has been carried out as part of a larger effort whose aim was the monitoring of human exposure to organic air pollutants. The aldehydes measured in this study are in the range C 1 ᎐C 8 , identified using a HPLC method with gradient elution and UV detection and a LC-APCI-MS method. The relative variations of the concentrations of aldehydes and of other measured pollutants during the studied periods were investigated. The contribution of outdoor environment to the average human daily intake of formaldehyde has been evaluated.
2. Materials and methods 2.1. Sampling strategy Ambient air samples were collected on 11᎐18 January 1999 at five urban locations in the northwest area of Milan wLegnano ŽSavonarola, Town Hall., Bollate ŽRosselli, Town Hall., Parabiago ŽSpagliardi.x. In Parabiago air samples were also collected in June and July 1999. Air samples from the rural-industrial area ŽBoffalora. were collected in August 1998 and in January 1999. At each site the sampling duration was 24 or 72 h Ž24 h from Monday to Thursday and 72 h from Friday to Sunday. if not otherwise specified. 2.2. Materials All solvents employed were HPLC-grade. The carbonyl 2,4-dinitrophenylhydrazine ŽDNPH. derivatives and the calibration standard ŽCarbonyl-DNPH Mix 1. containing 13 components ŽDNPH derivatives of acetaldehyde, acetone, acrolein, benzaldehyde, 2-butanone, nbutyraldehyde, crotonaldehyde, formaldehyde, hexanaldehyde, methacrolein, propionaldehyde, p-tolualdehyde, valeraldehyde. were purchased from Supelco. 2.3. Sampling system and analytical procedure The diffusive sampling cartridges Radiello purchased from Fondazione S. Maugeri ŽPadova.
were made of a 100᎐mesh s.s. net cylindrical chemi-adsorbing cartridge, o.d. 5.9 mm, containing 900 mg of 35᎐50 mesh 2,4-dinitrophenylhydrazine coated fluorisil. Following sample collection, the cartridges were eluted with 2 ml of acetonitrile. The acetonitrile extracts were analysed by liquid chromatography as described below. Aldehydes were identified in 57 air samples. 2.3.1. HPLC-UV analysis Each acetonitrile solution of carbonyl-DNPH standards and of air samples were analysed by liquid chromatography ŽLC. with UV detection ŽHewlett Packard Model 1050.. The column used was a 5-m C 18 Hypersil ŽHP. Ž250 mm length = 4.6 i.d... Separations were carried out at 25⬚C using the following mobile-phase gradient: flow rate, 1 mlrmin; 60% solvent A, 30% solvent B and 10% solvent C for 15 min Žsolvent A, water; solvent B, acetonitrile; solvent C, THF.; from 60 to 30% solvent A, 10% solvent C constant, within 25 min; then 5 min isocratic. The detection wavelength was 360 nm. The absorbance at the given wavelength Žpeak height or peak area. of five standard mixtures of DNPH-derivatives of aldehydes were used to construct the external calibration curves employed to measure the concentration of DNPH-derivatives of aldehydes in the ambient air samples. The concentrations of DNPH-derivatives of aldehydes in blank cartridges were measured. Analyses of blank cartridges yielded a quantity of formaldehyde lower than 0.1 g and of other aldehydes lower than 0.001 g. Blank correction was carried out for each analytical batch. Analytical precision was 1.5᎐2.5% at the 0.50 grml level. The limit of detection was 0.5 ng. 2.3.2. LC-APCI-MS analysis 2.3.2.1. Equipment. Hewlett Packard series 1100 MSD liquid chromatograph ŽPalo Alto, CA, USA. with a Quaternary Pump, an injector with a 20 l loop and APCI-MS detection. The column used was a 5-m C 18 Hypersil ŽHP. Ž250 mm length = 4.6 i.d... Separations were carried out at 25⬚C using the following binary mobile-phase gradient:
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
flow rate, 1 mlrmin; 50% solvent A, 50% solvent B for 10 min Žsolvent A, water; solvent B, acetonitrile.; from 50 to 30% solvent A, within 25 min; from 30 to 20% solvent A, within 10 min, then 5 min isocratic. 2.3.2.2. Optimization of LC-APCI-MS. The working conditions for the APCI were the following: drying nitrogen heated to 350⬚C and injected in the capillary region at a flow rate of 4 lrmin; the corona current was 25 A and the capillary voltage was 4000 V. An APCI negative ion mode ŽNI. was used and full scan data acquisition was performed scanning from m r z 90 to 500 to obtain the molecular ions wM-Hxy for each compound ŽTable 1.. The identification of DNPH-derivative of aldehydes in environmental samples was carried out using selected ion monitoring-negative ion acquisition mode ŽSIM-NI. in order to obtain lower detection limits. Table 1 summarizes the wM-Hxmasses of DNPH-derivatives of carbonyls identified.
3. Results and discussion 3.1. Diffusi¨ e sampling and HPLC-UVr LC-APCIMS analysis of ambient air samples The aim of this study was the evaluation of the Table 1 Molecular mass series of DNPH-Carbonyl derivatives DNPH derivative of:
MW
Molecular ion wM-Hxy
Formaldehyde Acetaldehyde Acetone Acrolein Propanal Crotonaldehyde Methacrolein 2-Butanone n-Butanal Benzaldehyde n-Pentanal m-Tolualdehyde n-Hexanal
210 224 238 236 238 250 250 252 252 286 266 300 280
209 223 237 235 237 249 249 251 251 285 265 299 279
13
extent of 24᎐72 h average human exposure to aldehydes by inhalation route. Therefore, diffusive sampling was preferred to pumped sampling in order to estimate the levels of carbonyl compounds in air. Moreover the overall uncertainty Žsampling q analysis . of diffusive samplers is reported to be slightly lower than that obtained with pumped sampling w5x. All ambient air samples contained many carbonyls. The HPLC-UV method allowed the separation of all the components of the standard mixture employed to build the calibration curve. However, during this study our interest was devoted to measure the concentration of the following aldehydes: formaldehyde, acetaldehyde, propanal, crotonaldehyde, n-butanal, n-pentanal, benzaldehyde, m-tolualdehyde, hexanal. Acrolein was identified in the air samples, however, the concentrations are not reported in this study, because sampling of acrolein on DNPH cartridge is usually reported to underestimate the true value w5x. The APCI in the negative ion mode generated mass spectra with only the wM-Hxy ion present in the operative conditions used. This technique gave independent confirmation of carbonyl structure for the aldehydes identified via HPLC-UV. In the chromatographic method employed in the LCAPCI-MS acetone and acrolein coeluted, however, they were easily identified from the different molecular ions ŽFig. 1.. LC-APCI-MS allowed the identification of carbonyl compounds in air extracts not easily revealed via HPLC-UV w6,7x. Many LC-MS chromatograms of air samples showed a signal between the signals of acetaldehyde and acetoneracrolein, whose APCI spectrum showed a wM-Hxy ion of m r z 363 as reported by other authors. It has been suggested to be a ‘reaction product between 2,4-dinitrophenylhydrazone and 2,4-dinitrochlorobenzene’ produced on-cartridge in the presence on nitrogen dioxide and HCl w7x. 3.2. Winter samplings During the week 11᎐18 January 1999 the sampling of ambient air samples and the measurements of the concentration of aldehydes were performed in five urban locations ŽLegnanor
B.P. Andreini et al. r Microchemical Journal 67 (2000) 11᎐19
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Fig. 1. HPLC-MS base peak chromatogram obtained by APCI-SIM-NI of the standard mixture of DNPH carbonyls. Table 2 Average carbonyl concentrations on 11᎐18 January 1999 Urban
Formaldehyde Acetaldehyde Propanal Crotonaldehyde n-Butanal Benzaldehyde n-Pentanal m-Tolualdehyde Hexanal Total aldehydes
BollateRosselli Žgrm3 .
Bollate Town Hall Žgrm3 .
Legnano Savonarola Žgrm3 .
Legnano Town Hall Žgrm3 .
Parabiago Žgrm3 .
Rural-industrial Boffalora Žgrm3 .
8.0 Ž"0.8. 5.1 Ž"2. 0.7 Ž"0.5. - 0.5 - 0.5 - 0.5 - 0.5 2.2 Ž"0.9. - 0.5 16.7 Ž"3.4.
9.8 Ž"1.8. 6.8 Ž"0.9. 1.2 Ž"0.2. - 0.5 - 0.5 0.5 Ž"0.5. - 0.5 - 0.5 - 0.5 19.0 Ž"3.7.
9.5 Ž"1.9. 6.5 Ž"1.2. 1.3 Ž"0.2. - 0.5 0.5 Ž"0.5. - 0.5 1.1 Ž"1.1. 2.3 Ž"0.7. - 0.5 25.2 Ž"4.1.
15.7 Ž"17.5. 7.3 Ž"8.4. 1.6 Ž"1.9. - 0.5 0.8 Ž"1.7. 1.6 Ž"2.1. - 0.5 3.1 Ž"2.8. - 0.5 30.7 Ž"35.5.
9.5 Ž"3.1. 6.1 Ž"1.6. 2.4 Ž"2.5. - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 17.9 Ž"4.8.
5.9 Ž"1.3. 4.5 Ž"1.3. 0.6 Ž"0.6. - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 - 0.5 11.7 Ž"2.9.
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Savonarola and Town Hall, BollaterRosselli and Town Hall, ParabiagorSpagliardi. and in a ruralindustrial location ŽBoffalora.. Formaldehyde, acetaldehyde and propanal were present in almost
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all samples, however, crotonaldehyde was always absent. The average values and standard deviations of the concentrations of all aldehydes measured in
Fig. 2. Ambient concentrations of Žfrom top to bottom. formaldehyde, acetaldehyde, propanal, m-tolualdehyde at Žfrom left to right. Bollate-Rosselli, Bollate-Town Hall, Legnano-Savonarola, Legnano-Town Hall, 11᎐18 January 1999. ŽSampling of 15 January is a 72-h one..
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the winter week are listed in Table 2. Ambient concentrations of four of the carbonyls studied here are shown in time series in Fig. 2: formaldehyde, acetaldehyde, propanal and m-tolualdehyde Žpentanal and benzaldehyde were seldom present.. m-Tolualdehyde is not shown in Fig. 3. The temporal variation of formaldehyde and of acetaldehyde in each location is very similar. Moreover, the same temporal variation of aldehydes is present in four out of six locations. Usually a maximum is present on 14 January ŽThursday. and a minimum is present in the 72 h sampling Ž15᎐18 January.. The variation of concentration of all aldehydes in Legnano is slightly different from the other locations, in particular Legnano Town Hall, which presented a severe episode of smog pollution on 12 January. In fact, high concentrations of several other pollutants were found on that day Žbenzene, toluene, particulate, benzow axpyrene.. Formaldehyde was the most abundant aldehyde in all samples and accounted for 50% of the total aldehydes concentrations measured in most samples. Ambient levels of formaldehyde ranged from 4.1 to 53.4 grm3 at the six locations. The week average values ranged from 8.0 to 15.7 grm3 at the five urban locations; the average value in the
rural-industrial location was 11.7 grm3. Acetaldehyde concentrations ranged from 2.1 to 25.7 grm3 , the rural-industrial location presenting the lowest average value. Acetaldehyde accounted for 25᎐45% of the total ambient aldehydes concentration at the urban locations. The higher molecular weight carbonyls accounted for a modest fraction of total aldehydes. The meteorological conditions Žtemperature, wind speed, duration and amount of rainfall . had a strong influence on concentrations of all pollutants: as expected, windy and rainy days Ž11 January. presented the lowest concentrations of pollutants, on the other hand sunny days, low wind speed and stable atmospheric conditions induced an increase of the concentration of aldehydes during the week until 14 January. Fig. 4 shows the different variation of total measured aldehydes with respect to meteorological conditions in the rural and in the urban areas. In the latter primary emissions from mobile sources had a strong influence on the levels of aldehydes even in rainy days. This effect is probably related to a limited scavenging effect in the urban area. A typical reduction of total carbonyl concentrations Žsee Fig. 4. in all locations Žexcept at Bollate-Rosselli. is present during the week-end,
Fig. 3. Ambient concentrations of Žfrom top to bottom. formaldehyde, acetaldehyde, propanal, m-tolualdehyde at Parabiago and Boffalora, 11᎐18 January 1999.
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confirming traffic as a major source of emissions in the north-west area of Milan. Moreover, the entity of reduction is different in the six locations according to the local traffic situation. 3.3. Summer sampling Sampling of carbonyls was performed in the rural-industrial location for three weeks in summer 1998 Ž16 July᎐6 August. and in the urban location, Parabiago-Spagliardi, for 2 weeks in 1999 Ž12᎐23 July, 23᎐30 August.. Ambient concentrations of four of the carbonyls studied in 1998 are shown in time series in Fig. 5a. The temporal variation of formaldehyde and acetaldehyde at Boffalora in 1999 is reported in Fig. 5b. The average values and standard deviations of the concentrations of all aldehydes measured in the two locations are listed in Table 3. Ambient levels of formaldehyde accounted for 16᎐92% of total aldehydes concentration in Boffalora, for 30᎐46% in Parabiago; they ranged from 4.6 to 15.9 grm3 in Boffalora, average value being 7.5 grm3, and from 6 to 12.5 grm3 in Parabiago, average level being 8.6 grm3. Acetaldehyde accounted for 7᎐42% in Boffalora Žrange: 1.3᎐6.7 grm3 , average: 4.5 grm3 . and 42᎐62% in Parabiago Žrange: 6.4᎐25 grm3 , average: 12.8 grm3 .. Meteorological conditions and week-end reduction of traffic strongly influence the summer concentrations of aldehydes as already observed in winter measurements. In fact lower concentra-
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tions of carbonyls were observed in rainy and windy days such as 27 and 28 July in comparison with the high values observed in the sunny days of the previous week in Boffalora. The week-end reduction of aldehyde levels is strongly evident in the two sunny weeks in Parabiago. At Boffalora all the aldehydes investigated were present in several samplings; n-butanal, n-pentanal and hexanal, absent in the winter sampling were randomly present in summer, therefore, the total aldehyde concentration is usually higher in summer than in winter. However, season does not seem to strongly affect average values of formaldehyde and acetaldehyde in Boffalora ŽStudent’s t-test: Ps 0.209.. Parabiago seems more affected by seasonal differences, in particular acetaldehyde concentrations are higher in summer than in winter. In relation to the observed data the contribution of photochemical production to aldehydes levels resulted more evident during summer months. In all locations benzene, toluene, ethylbenzene and xilene ŽBTEX. were measured in ambient samplings in parallel to aldehyde samplings. The temporal variation of total BTEX concentration was very similar to that of formaldehyde, as described in Fig. 6 ŽBoffalora in 1998.. This variation is typical of all locations and of each period. 3.4. Toxicological e¨ aluation The collected data are a starting point to evalu-
Fig. 4. Daily total measured aldehydes at Bollate-Rosselli, Bollate-Town Hall, Legnano-Savonarola, Legnano-Town Hall, Parabiago and Boffalora, 11᎐18 January 1999. Note meteorological situations on x-axis.
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Table 3 Average carbonyl concentrations in Boffalora, summer 1998 and Parabiago, summer 1999
Formaldehyde Acetaldehyde Propanal Crotonaldehyde n-Butanal Benzaldehyde n-pentanal m-Tolualdehyde Hexanal Total aldehydes
Urban Parabiago Žgrm3 .
Rural-industrial Boffalora Žgrm3 .
8.9 Ž"1.9. 13.7 Ž"5.7. 1.1 Ž"0.2. - 0.5 1.1 Ž"0.4. - 0.5 - 0.5 - 0.5 - 0.5 24.8 Ž7.9.
7.5 Ž"2.7. 4.5 Ž"1.7. 2.0 Ž"2.8. - 0.5 1.2 Ž"1.5. - 0.5 - 0.5 - 0.5 - 0.5 15.8 Ž"6.2.
ate the risk associated to outdoor exposure to aldehydes for people living in the investigated area. Table 2 and Table 3 summarize the average concentrations of aldehydes in a typical winter week presenting different atmospheric events and in a summer period typical of Pianura Padana, high temperature and humidity, low wind speed and sporadic rain. The levels of formaldehyde in the rural-industrial location are typical of areas not directly
interested by specific emissions and are mostly due to traffic emissions, as the urban levels in winter and in summer. The concentrations of all aldehydes during the week-end could be considered the base level of human exposure in winter and in summer. Formaldehyde is ubiquitous: indoor levels are reported to range from 10 to 4000 grm3 ; the contribution of various atmospheric environments to the average human daily intake has been calculated to be 0.02 mgrday for outdoor air in the investigated area and for similar areas 3. Therefore, outdoor exposure in the north-west area of Milan is a minimal fraction of total human exposure. The toxicological approach suggests that the levels of formaldehyde found in this area should not cause any acute toxic effect and any chronic effect, however, epidemiological studies need to be performed to support this hypothesis. Levels of acetaldehyde are usually lower than 10 grm3, except for the urban location in summer. These levels should not cause irritant effect or acute or chronic effects. In fact on the basis of data on irritancy in humans, a tolerable concentration of 2 mgrm3 has been derived; however, with respect to the induction of tu-
Fig. 5. Daily values for aldehydes observed at Ža. Boffalora in summer 1998 and Žb. Parabiago in summer 1999.
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Fig. 6. Variation with time of total aldehydesŽleft. and total aromatic compounds Žright. at Boffalora in summer 1998.
mours, the concentrations associated with a 10 5 excess lifetime risk are 11᎐65 grm3 w8x.
4. Conclusions The HPLC-UV and LC-APCI-MS negative ion mode methods were employed to evaluate the presence of aldehydes in ambient air samples. By-products were identified in the samples through the APCI-NI method. The concentration of aldehydes in the north-west area of Milan were higher in the urban locations with respect to the rural-industrial one. Concentrations were slightly higher in summer than in winter. The measured levels of formaldehyde and acetaldehyde suggested that outdoor exposure is a minimal fraction of the daily human exposure. These levels should not cause any acute or chronic toxic effect on humans on the basis of a toxicological approach. However, an epidemiological study needs
to be performed in that area to evaluate the contribution of low concentrations of aldehydes in presence of other micropollutants such as aromatic compounds, ozone and nitrogen oxides. References w1x A. Vairavamurthy, J.M. Roberts, L. Newman, Atmos. Environ. A 26 Ž1992. 1965. w2x P.D. Lighfoot, R.A. Cox, J.N. Cowley et al., Atmos. Environ A 25 Ž10. Ž1992. 1805. w3x Formaldehyde, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 62, IARC, Lyon, 1995 and references therein. w4x Acetaldehyde, IARC Monographs on the evaluation of carcinogenic risks to humans, vol. 36, IARC, Lyon, 1985 and references therein. w5x E. Goelen, M. Lambrechts, F. Geyskens, Analyst 122 Ž1997. 411. w6x E. Grosjean, D. Grosjean, M.P. Fraser, G.R. Cass, Environ. Sci. Technol. 30 Ž1996. 2687. w7x S. Kolliker, M. Oehme, C. Dye, Anal. Chem. 70 Ž1998. 1979. w8x WHO, Acetaldehyde Environmental Health Criteria Vol. 167. Geneva. IPCS Ž1995. and references therein.