Evaluation of the mutagenicity of combustion particles from several common biomass fuels in the Ames/Salmonella microsome test

Mutagenicity and Lung Toxicity of Smoldering vs. Flaming Emissions from Various Biomass Fuels: Implications for Health Effects from Wildland Fires

BACKGROUND

The increasing size and frequency of wildland fires are leading to greater potential for cardiopulmonary disease and cancer in exposed populations; however, little is known about how the types of fuel and combustion phases affect these adverse outcomes.

OBJECTIVES

We evaluated the mutagenicity and lung toxicity of particulate matter (PM) from flaming vs. smoldering phases of five biomass fuels, and compared results by equal mass or emission factors (EFs) derived from amount of fuel consumed.

METHODS

A quartz-tube furnace coupled to a multistage cryotrap was employed to collect smoke condensate from flaming and smoldering combustion of red oak, peat, pine needles, pine, and eucalyptus. Samples were analyzed chemically and assessed for acute lung toxicity in mice and mutagenicity in Salmonella.

RESULTS

The average combustion efficiency was 73 and 98% for the smoldering and flaming phases, respectively. On an equal mass basis, PM from eucalyptus and peat burned under flaming conditions induced significant lung toxicity potencies (neutrophil/mass of PM) compared to smoldering PM, whereas high levels of mutagenicity potencies were observed for flaming pine and peat PM compared to smoldering PM. When effects were adjusted for EF, the smoldering eucalyptus PM had the highest lung toxicity EF (neutrophil/mass of fuel burned), whereas smoldering pine and pine needles had the highest mutagenicity EF. These latter values were approximately 5, 10, and 30 times greater than those reported for open burning of agricultural plastic, woodburning cookstoves, and some municipal waste combustors, respectively.

CONCLUSIONS

PM from different fuels and combustion phases have appreciable differences in lung toxic and mutagenic potency, and on a mass basis, flaming samples are more active, whereas smoldering samples have greater effect when EFs are taken into account. Knowledge of the differential toxicity of biomass emissions will contribute to more accurate hazard assessment of biomass smoke exposures. https://doi.org/10.1289/EHP2200.

Elevated Exposures to Polycyclic Aromatic Hydrocarbons and Other Organic Mutagens in Ottawa Firefighters Participating in Emergency, On-Shift Fire Suppression

Occupational exposures to combustion emissions were examined in Ottawa Fire Service (OFS) firefighters. Paired urine and dermal wipe samples (i.e., pre- and post-event) as well as personal air samples and fire event questionnaires were collected from 27 male OFS firefighters. A total of 18 OFS office workers were used as additional controls. Exposures to polycyclic aromatic hydrocarbons (PAHs) and other organic mutagens were assessed by quantification of urinary PAH metabolite levels, levels of PAHs in dermal wipes and personal air samples, and urinary mutagenicity using the Salmonella mutagenicity assay (Ames test). Urinary Clara Cell 16 (CC16) and 15-isoprostane F_2t (8-iso-PGF_2α) levels were used to assess lung injury and overall oxidative stress, respectively. The results showed significant 2.9- to 5.3-fold increases in average post-event levels of urinary PAH metabolites, depending on the PAH metabolite (p < 0.0001). Average post-event levels of urinary mutagenicity showed a significant, event-related 4.3-fold increase (p < 0.0001). Urinary CC16 and 8-iso-PGF_2α did not increase. PAH concentrations in personal air and on skin accounted for 54% of the variation in fold changes of urinary PAH metabolites (p < 0.002). The results indicate that emergency, on-shift fire suppression is associated with significantly elevated exposures to combustion emissions.

Mutagenicity of particle emissions from solid fuel cookstoves: A literature review and research perspective

Household solid fuel use is a major source of many air pollutants causing severe air pollution and adverse health outcomes. In evaluation of health impacts of household air pollution, it is essential to characterize toxic properties like mutagenicity of residential fuel combustion emissions and exposure assessments. Mutagenicity of emissions from solid fuel cookstoves were analyzed through a literature review. T98 and TA100 strains are two most widely used strains in mutagenic Ames test, and results for these two strains are generally positively correlated though they have different endpoints. Direct and indirect mutagenic activities are positively correlated, and statistically insignificantly different though indirect mutagenic emissions are apparently higher. Mutagenicity emission factors on the basis of fuel energy (MJ) or useful energy delivered (MJd) for solid fuel cookstoves vary in nearly 3 orders of magnitude, ranging from 3.0×10⁴ rev./MJd to 1.8×10⁷ rev./MJd (or 1.1×10⁴ rev./MJ to 4.2×10⁶ rev./MJ). Low mutagenic emissions are reported for high efficiency stoves such as a forced-draft one. Mutagenicity emission factors are positively correlated with emissions of PM_2.5. Relationship between mutagenicity and polycyclic aromatic hydrocarbons (PAHs) emissions is inconsistent among studies as PAHs are minor fractions of toxic organics contributing to the total mutagenicity. Generally, studies on mutagenicity of emissions from household cookstoves are very limited, and future studies are encouraged on mutagenic emissions from different fuel types and household stoves, evaluation of mutagenic activities of both gaseous and particulate emissions, and toxicology and exposure assessments of household air pollution.

Human urinary mutagenicity after wood smoke exposure during traditional temazcal use

In Central America, the traditional temazcales or wood-fired steam baths, commonly used by many Native American populations, are often heated by wood fires with little ventilation, and this use results in high wood smoke exposure. Urinary mutagenicity has been previously employed as a non-invasive biomarker of human exposure to combustion emissions. This study examined the urinary mutagenicity in 19 indigenous Mayan families from the highlands of Guatemala who regularly use temazcales (N = 32), as well as control (unexposed) individuals from the same population (N = 9). Urine samples collected before and after temazcal exposure were enzymatically deconjugated and extracted using solid-phase extraction. The creatinine-adjusted mutagenic potency of urine extracts was assessed using the plate-incorporation version of the Salmonella mutagenicity assay with strain YG1041 in the presence of exogenous metabolic activation. The post-exposure mutagenic potency of urine extracts were, on average, 1.7-fold higher than pre-exposure samples (P < 0.005) and also significantly more mutagenic than the control samples (P < 0.05). Exhaled carbon monoxide (CO) was ~10 times higher following temazcal use (P < 0.0001), and both CO level and time spent in temazcal were positively associated with urinary mutagenic potency (i.e. P < 0.0001 and P = 0.01, respectively). Thus, the wood smoke exposure associated with temazcal use contributes to increased excretion of conjugated mutagenic metabolites. Moreover, urinary mutagenic potency is correlated with other metrics of exposure (i.e. exhaled CO, duration of exposure). Since urinary mutagenicity is a biomarker associated with genetic damage, temazcal use may therefore be expected to contribute to an increased risk of DNA damage and mutation, effects associated with the initiation of cancer.

Mutagenicity assessment of aerosols in emissions from wood combustion in Portugal

Polycyclic aromatic hydrocarbon (PAH) extracts of fine particles (PM(2.5)) collected from combustion of seven wood species and briquettes were tested for mutagenic activities using Ames test with Salmonella typhimurium TA98 and TA100. The woods were Pinus pinaster (maritime pine), Eucalyptus globulus (eucalypt), Quercus suber (cork oak), Acacia longifolia (golden wattle), Quercus faginea (Portuguese oak), Olea europea (olive), and Quercus ilex rotundifolia (Holm oak). Burning experiments were done using woodstove and fireplace, hot start and cold start conditions. A mutagenic response was recorded for all species except golden wattle, maritime pine, and briquettes. The mutagenic extracts were not correlated with high emission factors of carcinogenic PAHs. These extracts were obtained both from two burning appliances and start-up conditions. However, fireplace seemed to favour the occurrence of mutagenic emissions. The negative result recorded for golden wattle was interesting, in an ecological point of view, since after confirmation, this invasive species, can be recommended for domestic use.

Physical-chemical and microbiological characterization, and mutagenic activity of airborne PM sampled in a biomass-fueled electrical production facility

Biomass combustion is used in heating and electric power generation in many areas of the world. Airborne particulate matter (PM) is released when biomass is brought to a facility, stored, and combusted. Occupational exposure to airborne PM within biomass-fueled facilities may lead to health problems. In March and August of 2006, airborne PM was collected from a biomass-fueled facility located in Denmark. In addition, source-specific PM was generated from straw and wood pellets using a rotating drum. The PM was analyzed for polycyclic aromatic hydrocarbons (PAHs), metals, microbial components, mutagenic activity, and ability to generate highly reactive oxygen species (hROS) in cell-free aqueous suspensions. PM collected from the boiler room and the biomass storage hall had higher levels of mutagenic activity, PAHs and metals, and a higher hROS generating potential than the source specific PM. The mutagenic activity was generally more potent without S9 activation, and on the metabolically enhanced strain YG1041, relative to TA98. Significant correlations were found between mutagenicity on YG1041 (without S9) and PAH concentration and mutagenicity on YG1041 (with S9) and hROS generating ability. PM collected in March was more toxic than PM collected in August. Overall, airborne PM collected from the facility, especially that from the boiler room, were more toxic than PM generated from straw and wood chips. The results suggest that exposure to combustion PM in a biomass-fueled facility, which likely includes PM from biomass combustion as well as internal combustion vehicles, may contribute to an elevated risk of adverse health effects.

Cytogenetic biomonitoring of Indian women cooking with biofuels: micronucleus and chromosomal aberration tests in peripheral blood lymphocytes

India currently has the largest number of indoor air pollution-related health problems in the world, with three-quarters of its households burning wood, cowdung, or crop residues ("traditional" biomass fuels) for cooking, and the remainder using kerosene and relatively clean-burning liquefied petroleum gas (LPG). Combustion of these fuels produces various pollutants that may cause serious health effects in exposed populations. In this study, the micronucleus (MN) and chromosomal aberration (CA) assays were used to evaluate the relative amounts of DNA damage produced by the use of these cooking fuels. Cytogenetic evaluation of 179 female subjects showed a significant increase in both MN and CA frequency in blood lymphocytes from users of biomass-fuels in comparison to lymphocytes from LPG users (used as a reference population). The relative MN and CA frequencies for the users of the various fuels decreased in the order cowdung > cowdung/wood >/= wood > kerosene >/= LPG. Further, the results indicated an effect of subject age, and the duration of exposure on the MN and CA frequencies in biomass fuel users. Age had no significant effects on the genotoxicity responses in subjects with </=10 years of exposure to either biomass fuels or LPG, but in subjects using biomass fuels for >10 years, CA and MN frequencies were higher in older individuals (>30 years of age) than younger subjects. Regardless of age, subjects burning biomass fuels had higher MN and CA frequencies than LPG users only when exposures were of at least 5 years duration. These results indicate that burning biomass-based fuels increases the frequency of cytogenetic alterations in blood lymphocytes of exposed populations, possibly because of exposure to the various noxious gases and toxic substances present in biomass fuels. These cytogenetic markers could be used in the field to assess the genotoxic consequences of burning various cooking fuels and for early detection of genetic abnormalities in people exposed to various pollutants and toxicants.

Mutagens in indoor air particulate

Twenty-seven extracts of airborne particulate from domestic environments, both in the absence of sources of pollution and during activities such as smoking tobacco, using a fireplace, and cooking using grills and barbecues, and eight control samples of outdoor particulate were tested using the Salmonella/microsome assay on strains TA98 and TA98NR. Dust levels and mutagenic activity in the indoor environments turned out to be very low in the absence of polluting sources, with highest mean values in winter of less than 0.1 mg/m3 and 6 and 12 revertants/m3, respectively without and with S9. The specific mutagenic activity of indoor dust ranged from 22 and 137 revertants/mg, with a contribution of nitroarene compounds of about 50%, indicating that, in city indoor air, the main cause of background particulate pollution is very probably penetration of traffic fumes from the outside. In contrast, in a country house far from traffic, very low dust and mutagenicity levels were found, without the influence of nitroarene compounds. The presence of autochthonous polluting sources, such as tobacco smoke and fumes from cooking and wood or charcoal burning, greatly increased indoor dust levels, especially during cooking operations, which reached 25.5 and 31.6 mg/m3. The particulate produced by the various indoor pollution sources showed varying specific mutagenic activities. The highest values were found for fumes produced by burning charcoal and wood, smoking tobacco, and cooking foods with high animal protein contents. Mutagens responsible were mainly direct-acting in the case of fumes from burning wood or charcoal, and required mammalian metabolic activation in the case of fumes from tobacco and meat, with a lower contribution (maximum 33%) of nitroarenes than in urban particulate.

Mutagenicity of wood smoke condensates in the Salmonella/microsome assay

Smoke condensates of woods used for food preservation and aromatization in Nigeria were tested for mutagenic activity using Salmonella typhimurium TA98 and TA100. The woods were: white mangrove (Avicennia nitida), red mangrove (Rhizophora racemosa), mahogany Khaya sp.), abura (Mitragyna ciliata), alstonia (Alstonia boonei) and black afara (Terminalia ivorensis). Cigarette tar was tested for comparison. The condensates induced dose-dependent increases in the number of His+ revertants mainly with S9 mix. With the exception of mahogany and cigarette smoke condensate, the smoke condensates induced more revertants/microgram condensate in TA100 than in TA98. The number of revertants/microgram condensate ranged between 0.04 and 0.9 for the wood smoke condensates and was 0.12 for the cigarette smoke in TA100. The range was between 0.1 and 0.30 for the wood smoke condensates and 0.18 revertants/microgram condensate for cigarette smoke condensate in TA98. Concentrations of 7 polycyclic aromatic hydrocarbons (PAHs) in the condensates were determined namely, pyrene, benzo[a]pyrene, benz[a]anthracene, benzo[k]fluoranthene, benzo[b]chrysene, benzo[g,h,i]perylene and dibenzo[a,e]pyrene. The condensates contained varying concentrations of the individual PAHs and those with higher concentrations generally showed greater mutagenic activities. However, the order of mutagenic potency in the bacterial strains differed from the order of PAH concentrations, which were lower than the concentrations at which they are reported to induce mutations. When 6 of the PAHs were mixed in the concentrations in which they were found in the individual condensates, the mixtures did not induce mutation so that the contribution of the PAHs to the mutagenic activities of the condensates could not be determined.