Table 1
VOC mixture in the air of the largest cities in the Mexican Republic.
| Monterrey [15] | Guadalajara [16] | México [14] | |||||||
|---|---|---|---|---|---|---|---|---|---|
| VOC | Origin/use | Maximal ppbV | VOC | Origin/use | Maximal ppbV | VOC | Origin/use | Maximal ppbV | |
| 1 | Ethanol | Industrial/fuel combustion | 150 | Propane | LP gas | 160 | Propane | LP gas | 28 |
| 2 | Propane | LP gas | 150 | Methylcyclo-pentane | Industrial | 70 | Acetone | Domestic product | 17 |
| 3 | 2-hexanone | Industrial | 105 | n-butane | LP gas | 38 | Ethanol | Fuel combustion | 15 |
| 4 | Acetone | Industrial | 60 | Acetone | Domestic use | 30 | n-butane | LP gas | 15 |
| 5 | 4-methyl-2-pentanone | Industrial/domestic product | 40 | Ethanol | Fuel combustion | 30 | Toluene | Fuel combustion | 8 |
| 6 | 2-propanol | Industrial/domestic products | 35 | 2-hexanone | Industrial | 30 | n-pentane | Fuel combustion/domestic product | 10 |
| 7 | Hexachloro-1,3-butadiene | Industrial | 35 | 2-propanol | Industrial/domestic product | 25 | Isopentane | Fuel combustion/domestic product | 8 |
| 8 | 1,4-dichlorobenzene | Industrial | 30 | Toluene | Fuel combustion/domestic product | 20 | n-hexane | Fuel combustion | 6 |
| 9 | 1,2,4-trimethylbenzene | Fuel combustion/industrial | 30 | Isobutane | LP gas | 18 | Ethylene | Domestic product/fuel combustion | 5 |
| 10 | n-butane | LP gas | 30 | 4-methyl-2-pentanone | Industrial/domestic product | 18 | Isobutane | LP gas | 5 |
| TOTAL VOC | Santa Catarina area | 1051 | TOTAL VOC | Average Whole City | 678.04 | TOTAL VOC | La Merced area | 605.5 | |
[i] TOTAL VOC – refers to the sum of all VOC measured; in the table, only the ten more abundant are presented.
Table 2
Potential contribution of VOC to ozone formation according to their MIR* factors in Monterrey and Mexico City.
| Monterrey (Santa Catarina area) [15] | Mexico City (La Merced area) [14] | ||
|---|---|---|---|
| VOC | Potential ozone formation (ppbV) | VOC | Potential ozone formation (ppbV) |
| Ethanol | 233.5 | Toluene | 72.8 |
| Acrolein | 132 | o-xylene | 42.8 |
| Methyl-metacrylate | 108.7 | Ethanol | 21.4 |
| Toluene | 101.0 | Propylene | 21.2 |
| Propylene | 82 | Ethylene | 20.8 |
| 1,2,4-trimethylbenzene | 79.5 | 1,2,4-trimethylbenzene | 17.5 |
| o-xylene | 79.4 | m-xylene | 14.5 |
| m-xylene | 78.4 | n-hexane | 11.9 |
| p-xylene | 71.8 | Isopentane | 11.7 |
| 1-pentene | 64.9 | n-butane | 11.5 |
| 4-methyl-2-pentanone | 59.2 | 1,3,5-trimethylbenzene | 9.7 |
| Propane | 57.8 | 1,3-butadiene | 9.7 |
| Naphthalene | 55.7 | Propane | 8.9 |
| 1,3,5-trimethylbenzene | 50.9 | p-xylene | 8.7 |
| n-hexane | 50.3 | Ethylbenzene | 7.7 |
| TOTAL POF | 1,305.1 | TOTAL POF | 290.8 |
[i] * Maximum Incremental Reactivity.
POF – potential ozone formation.
Table 3
Concentrations of BTEX in different studies (µg/m3).
| *Benzene µg/m3 | Toluene µg/m3 | Ethylbenzene µg/m3 | o-xylene µg/m3 | m, p-xylene µg/m3 | Country | Type of measurement | Reference |
|---|---|---|---|---|---|---|---|
| 1.21 | 14.33 | 2.55 | 2.16 | 5.97 | USA population | Personal exposure | [66] |
| 0.63 | 1.09 | 0.32 | 0.26 | . | Canada | Outdoor levels | [67] |
| 0.78–0.88 | . | . | . | . | Stenungsund, Sweden, Petrochemical area | Outdoor levels | [68] |
| 2.15 | 6.83 | 1.28 | 1.46 | 3.56 | USA population | Outdoor levels | [21] |
| 3.64 | 19.2 | 2.78 | 2.87 | 8.07 | USA population | Personal exposure | [21] |
| 1.5–6.95 | 7.17–26.9 | 0.59–2.06 | 0.94–4.16 | 3.07–13.3 | Review of studies in the world | Outdoor levels | [10] |
| 1.21–2.8 | 14.33 | 2.55 | 2.16 | 5.97 | Review of studies in the world | Personal exposure | [10] |
| 15.07 | 139.35 | 24.68 | 13.39 | 27.88 | Kwai Chung in Hong Kong industrial area | Outdoor levels | [8] |
| 0.7–3.5 | 2.3–6.0 | 0.4–5 | . | 1.9–2.3 | Viseu, Portugal | Outdoor levels | [40] |
| 13.42 | 18.9 | 1.8 | 2.3 | 10.91 | La Plata industrial area, Argentina | Outdoor levels | [69] |
| 0.58–3.0 | 2.8–5.9 | 0.2–1.6 | 0.26–1.3 | 1.3–3.5 | Curitiba, Brazil, suburban area | Outdoor levels | [70] |
| 0.58–6.0 | 4.3–73 | 0.19–2.5 | 0.24–45 | 1.3–6.9 | Curitiba, Brazil, suburban area | Personal exposure | [70] |
| 5.9 | 37.9 | 5 | 5.9 | 14.9 | Mexico City | Outdoor levels | [24] |
| 10.6 | 86.1 | 8.1 | 9.1 | 25.2 | Mexico City | Personal exposure | [24] |
| 2.18–3.7 | 17.17–46.9 | 2.4–7.2 | 2.8–11.3 | 3.8–11.7 | Mexico City | Outdoor levels | [17] |
| 1.1–5.3 | 2.3–14.0 | 0.4–2.2 | 0.5–3.2 | 1.4–8.0 | Industrial area, Tlaxcala, Mexico | Outdoor levels | [74] |
| 0.03 | 5 | 1 | 0.1 | 0.1 | USA | Outdoor levels | Rfc (mg/m3) [71] |
| 1.01 | 6.95 | 1.5 | 1.5 | 4.1 | Global | Personal exposure | ** µg/m3 |
[i] * Bold numbers in the benzene column represent increased risk of leukemia for those populations.
** Lowest concentrations found to produce health effects [10].
Figure 1
Highest levels of benzene reported in urban and industrial areas, both in developed and developing countries. Notice the extraordinary low levels reported in urban Canada (left panel) and industrial Sweden (right panel). Industrial areas in Latin America are not continuously monitored for air quality, only great cities, but children and pregnant women live in these places where pollution is generally high. Urb-urban; pers-personal; PCh-petrochemical zone; Ind-industrial zone; PollRiv-polluted river.
Figure 2
Chemical structure of BTEX. Upper line: benzene, toluene and ethylbenzene. Lower line: orto-, meta- and para-xylene.
Figure 3
Probable pathways of benzene leukemogenic activity. These events might take place either in the fetal liver or in the infant bone marrow, or in both, to produce childhood leukemia (based on [10, 56]).
Table 4
VOC exposure and health effects in children.
| VOC studied | Place | Biomarker | Age | Health effects | Exposure concentrations | Reference |
|---|---|---|---|---|---|---|
| Benzene | Valencia, Spain, big city | Home outdoor and indoor levels | Infants | No conclusive relationship with respiratory illness was found | Outdoor levels: 0.5–3.61 µg/m3, i/o ratio: 0.3–26.08 µg/m3 (highest in winter) | [72] |
| BTEX, and other 37 VOC | Genoa, Italy, with petrochemical industry away from residential zone | Home outdoor levels | 6–10 years old | BTEX did not differ between zones. Higher risk of respiratory syndromes and absenteeism in children living in the industrial zone | 114.4 µg/m3 of total VOC in the industrial area vs. 80.7 µg/m3 in the residential area. Respiratory effects are attributed to o-xylene | [44] |
| Benzene, toluene, ethylbenzene, xylenes and formaldehyde | Viseu, Portugal, nonindustrial city | Forced expiratory volume (FEV), forced vital capacity (FVC). VOC levels indoors and outdoors | 7.3 ± 1.1 years old | Toluene levels, ethylbenzene and benzene exposure increases were associated with the need for medical intervention related with wheezing | 0.5–39.2 µg/m3 benzene levels in a year; 3.3–108.2 µg/m3 toluene levels; 0.6–60.6 µg/m3 ethylbenzene levels; 2.1–185.6 µg/m3 xylenes levels in a year | [40] |
| Benzene, toluene, xylenes, NO2 | Guamaré, Rio Grande do Norte, Brazil. City with petrochemical industry | Air quality monitoring station and respiratory symptoms in children | 0–14 years old | VOC were under acceptable levels. Significant associations were found between wheezing and the homes closer to highest VOC levels in air | Benzene levels 32.4 µg/m3; Toluene levels 18.8 µg/m3; Xylenes levels 18.1 µg/m3 | [43] |
| BTEX and other VOC, alkanes and cycloalkanes | La Plata, petrochemical zone compared to heavy traffic and nonpolluted areas | Forced expiratory volume (FEV), forced vital capacity (FVC). VOC levels outdoors | 6–12 years old | Children in the petrochemical area showed significantly more respiratory problems during the winter season, including asthma | Benzene levels 19.3 µg/m3; Toluene levels 19.1 µg/m3; Xylenes levels 9.6 µg/m3; Total VOC levels 102.1 µg/m3 | [42] |
| Benzene, toluene | Guangzhou, China, industrial city | 8-OHdG, t,t-muconic acid (t,t-MA), dihydroxybenzene, s-phenylmercapturic acid (S-PMA), s-benzylmercapturic | 3–6 years old | Co-exposure to benzene and toluene, plus HAP, induces additional DNA damage | Levels of t,t-MA: 2.6 to 381.16 µg/g creatinine; sum of all toluene and benzene metabolites: 25.09 to 1175.15 µg/g creatinine | [51] |
| Benzene | Kinshasa, Democratic Republic of Congo. Urban area | Phenylmercapturic acid (S-PMA) in urine | 1–5 and 6–14 years | S-PMA levels are 10X higher than those reported for Canadian kids. A level of 7.0 µg/L in urine is proposed as a reference value | S-PMA level of 7 µg/L urine was found as a geometric mean in children aged 6 to 14 years old | [35] |
| Benzene, toluene | Coatzacoalcos, Veracruz, México. Petrochemical and oil refinery city | t,t-muconic acid (t,t-MA) and hipuric acid (HA) in urine. Comet assay and hematologic parameters | 6–12 years old | Toluene and benzene metabolites did not exceed occupational levels. t,t-MA inversely correlated with hematocrit and hemoglobin values, as well as with red cell count | 44–5521 µg/g creatinine of t,t-MA; 0.03–2.12 g/g creatinine of HA | [50] |
| Benzene | Two urban-industrial areas in Buenos Aires, Argentina | t,t-muconic acid and benzene in air | 7–11 years old | t,t-MA 48.6 to 1367.8 µg/g creatinine, and benzene levels of 0.04 to 0.49 mg/m3 | [49] | |
| Benzene, toluene | San Luis Potosí, México. Urban area | t,t-muconic acid and hipuric acid in urine | 9.5 ± 4.0 (6–13.5) years old | t,t-MA levels of 35 to 850 µg/g creatinine; HA levels of 0.1 to 1.75 g/g creatinine. Under reference values for both exposures | [53] | |
| VOC | San Luis Potosí, México. Indigenous communities close to polluted rivers in a rural neglected area | t,t-muconic acid and 1-hydroxy-pyrene in urine | Children aged 7.5 ± 1.5 years old | t,t, MA: 38.4–4334 µg/g creatinine; 1-OHP: 0.02–94.1 µmol/mol creatinine; | [52] | |
| VOC of industrial and mobile sources | Atoyac River in Central México | Forty-two sampling stations in six zones along the river | All the population living in a strip of two kilometers measured from the banks of the river | They conclude that the loss of ecological equilibrium in the basin represents an immediate and future health risk for inhabitants on the banks | Concentrations were not disclosed; however, the river does not sustain macroscopic life | [73] |
| BTEX | Global-42 studies from around the world and several settings: industrial, urban, rural | Air levels, indoor, outdoor, personal and urinary metabolites | Prenatal to senescence | Developmental, immune function, reproductive, respiratory, hematological, cardiovascular disease | BTEX levels under reference values established by EPA | [10] |
[i] As a reference, ACGIH has recommended the following BEI for BTEX in occupational environment: benzene, S-PMA – 25 µg/g creatinine, t,t-MA – 500 µg/g creatinine; toluene, hippuric acid – 1.6 g/g creatinine, o-cresol – 0.3 mg/g creatinine.
Figure 4
Oxidative stress, gene regulation and cytotoxic effects due to exposure to BTEX. ROS-reactive oxygen species; FR-free radicals. Prx – peroxiredoxin; Trx – thioredoxin; GPXs – glutathione peroxidase.