Colin Finnegan

All Publications

• Exposure and health risks of benzene from combustion by gas stoves: A modelling approach in U.S. homes. Journal of hazardous materials Garg, A., Kashtan, Y., Nicholson, M., Finnegan, C. J., Lebel, E. D., Michanowicz, D. R., Shonkoff, S. B., Nadeau, K. C., Jackson, R. B. 2025; 492: 137986

  Abstract

  Natural gas and propane stoves emit benzene, a known carcinogen through combustion. This study evaluates population-level benzene exposure and associated health risks for the 6.3 million U.S. residents exposed to the top 5 % highest benzene-emitting gas stoves. We used the National Institute of Standards and Technology's CONTAM, a multizone indoor air quality model, to simulate benzene concentration distributions across 24 floorplans by integrating benzene emission rates with U.S. housing stock data. Health risks were assessed using the USEPA Health Risk Assessment methodology under scenarios of low, medium, and high stove usage with ventilated (open windows or/and hoods) and non-ventilated conditions. The results show that gas stove emissions significantly elevate cancer risks in homes with medium to high gas stove usage and inadequate ventilation. The cumulative Incremental Lifetime Cancer Risks (ILTCR) often exceeded the WHO safe threshold of 1E-06, particularly for children, whose ILTCR was 1.85 times higher (95 % CI: 1.43-2.12) than for adults in most of the high and medium gas stove usage scenarios. While cancer risks were elevated, non-cancer outcomes had hazard quotients < 1 in all scenarios. Ventilation mitigated risks, with high-efficiency (≥75 %) vented hoods notably reducing benzene exposure in kitchens. The study underscores the importance of addressing combustion-related indoor air pollutants to protect public health, particularly in households with limited ventilation.

  View details for DOI 10.1016/j.jhazmat.2025.137986

  View details for PubMedID 40158504

• Letter to the editor regarding: "Challenging unverified assumptions in causal claims: Do gas stoves increase risk of pediatric asthma?" Global epidemiology Nadeau, K. C., Kashtan, Y., Nicholson, M., Finnegan, C. J., Ouyang, Z., Garg, A., Lebel, E. D., Rowland, S. T., Michanowicz, D. R., Jackson, R. B. 2024; 8: 100172

  View details for DOI 10.1016/j.gloepi.2024.100172

  View details for PubMedID 39507817

• Downstream natural gas composition across US and Canada: implications for indoor methane leaks and hazardous air pollutant exposures ENVIRONMENTAL RESEARCH LETTERS Rowland, S. T., Lebel, E. D., Goldman, J. S. W., Domen, J. K., Bilsback, K. R., Ruiz, A., Jaeger, J. M., Hill, L. L., Kashtan, Y. S., Finnegan, C., Nicholson, M., Ouyang, Z., Jackson, R. B., Shonkoff, S. B. C., Michanowicz, D. R. 2024; 19 (6)

  View details for DOI 10.1088/1748-9326/ad416c

  View details for Web of Science ID 001249969800001

• Nitrogen dioxide exposure, health outcomes, and associated demographic disparities due to gas and propane combustion by U.S. stoves. Science advances Kashtan, Y., Nicholson, M., Finnegan, C. J., Ouyang, Z., Garg, A., Lebel, E. D., Rowland, S. T., Michanowicz, D. R., Herrera, J., Nadeau, K. C., Jackson, R. B. 2024; 10 (18): eadm8680

  Abstract

  Gas and propane stoves emit nitrogen dioxide (NO2) pollution indoors, but the exposures of different U.S. demographic groups are unknown. We estimate NO2 exposure and health consequences using emissions and concentration measurements from >100 homes, a room-specific indoor air quality model, epidemiological risk parameters, and statistical sampling of housing characteristics and occupant behavior. Gas and propane stoves increase long-term NO2 exposure 4.0 parts per billion volume on average across the United States, 75% of the World Health Organization's exposure guideline. This increased exposure likely causes ~50,000 cases of current pediatric asthma from long-term NO2 exposure alone. Short-term NO2 exposure from typical gas stove use frequently exceeds both World Health Organization and U.S. Environmental Protection Agency benchmarks. People living in residences <800 ft2 in size incur four times more long-term NO2 exposure than people in residences >3000 ft2 in size; American Indian/Alaska Native and Black and Hispanic/Latino households incur 60 and 20% more NO2 exposure, respectively, than the national average.

  View details for DOI 10.1126/sciadv.adm8680

  View details for PubMedID 38701214

  View details for PubMedCentralID PMC11068006

• Gas and Propane Combustion from Stoves Emits Benzene and Increases Indoor Air Pollution. Environmental science & technology Kashtan, Y. S., Nicholson, M., Finnegan, C., Ouyang, Z., Lebel, E. D., Michanowicz, D. R., Shonkoff, S. B., Jackson, R. B. 2023

  Abstract

  Exposure pathways to the carcinogen benzene are well-established from tobacco smoke, oil and gas development, refining, gasoline pumping, and gasoline and diesel combustion. Combustion has also been linked to the formation of nitrogen dioxide, carbon monoxide, and formaldehyde indoors from gas stoves. To our knowledge, however, no research has quantified the formation of benzene indoors from gas combustion by stoves. Across 87 homes in California and Colorado, natural gas and propane combustion emitted detectable and repeatable levels of benzene that in some homes raised indoor benzene concentrations above well-established health benchmarks. Mean benzene emissions from gas and propane burners on high and ovens set to 350 °F ranged from 2.8 to 6.5 μg min-1, 10 to 25 times higher than emissions from electric coil and radiant alternatives; neither induction stoves nor the food being cooked emitted detectable benzene. Benzene produced by gas and propane stoves also migrated throughout homes, in some cases elevating bedroom benzene concentrations above chronic health benchmarks for hours after the stove was turned off. Combustion of gas and propane from stoves may be a substantial benzene exposure pathway and can reduce indoor air quality.

  View details for DOI 10.1021/acs.est.2c09289

  View details for PubMedID 37319002

• Methane and NO<i>_x</i> Emissions from Natural Gas Stoves, Cooktops, and Ovens in Residential Homes (vol 56, pg 2529, 2022) ENVIRONMENTAL SCIENCE & TECHNOLOGY Lebel, E. D., Finnegan, C., Ouyang, Z., Jackson, R. B. 2022; 56 (10): 6791

  View details for DOI 10.1021/acs.est.2c02284

  View details for Web of Science ID 000804806300078

  View details for PubMedID 35467859

• Methane and NOx Emissions from Natural Gas Stoves, Cooktops, and Ovens in Residential Homes. Environmental science & technology Lebel, E. D., Finnegan, C. J., Ouyang, Z., Jackson, R. B. 1800

  Abstract

  Natural gas stoves in >40 million U.S. residences release methane (CH4)─a potent greenhouse gas─through post-meter leaks and incomplete combustion. We quantified methane released in 53 homes during all phases of stove use: steady-state-off (appliance not in use), steady-state-on (during combustion), and transitory periods of ignition and extinguishment. We estimated that natural gas stoves emit 0.8-1.3% of the gas they use as unburned methane and that total U.S. stove emissions are 28.1 [95% confidence interval: 18.5, 41.2] Gg CH4 year-1. More than three-quarters of methane emissions we measured originated during steady-state-off. Using a 20-year timeframe for methane, annual methane emissions from all gas stoves in U.S. homes have a climate impact comparable to the annual carbon dioxide emissions of 500 000 cars. In addition to methane emissions, co-emitted health-damaging air pollutants such as nitrogen oxides (NOx) are released into home air and can trigger respiratory diseases. In 32 homes, we measured NOx (NO and NO2) emissions and found them to be linearly related to the amount of natural gas burned (r2 = 0.76; p ≪ 0.01). Emissions averaged 21.7 [20.5, 22.9] ng NOx J-1, comprised of 7.8 [7.1, 8.4] ng NO2 J-1 and 14.0 [12.8, 15.1] ng NO J-1. Our data suggest that families who don't use their range hoods or who have poor ventilation can surpass the 1-h national standard of NO2 (100 ppb) within a few minutes of stove usage, particularly in smaller kitchens.

  View details for DOI 10.1021/acs.est.1c04707

  View details for PubMedID 35081712

• Low-intensity frequent fires in coniferous forests transform soil organic matter in ways that may offset ecosystem carbon losses. Global change biology Pellegrini, A. F., Caprio, A. C., Georgiou, K., Finnegan, C., Hobbie, S. E., Hatten, J. A., Jackson, R. B. 2021

  Abstract

  The impact of shifting disturbance regimes on soil carbon (C) storage is a key uncertainty in global change research. Wildfires in coniferous forests are becoming more frequent in many regions, potentially causing large C emissions. Repeated low-intensity fires can mitigate wildfire severity, but repeated combustion may decrease soil C unless compensatory responses stabilize soil organic matter. Here we tested how 30 years of decadal prescribed burning affected C and nitrogen (N) in plants, detritus, and soils in coniferous forests in the Sierra Nevada mountains, USA. Tree basal area and litter stocks were resilient to fire, but fire reduced forest floor C by 77% (-36.4 MgC ha-1 ). In mineral soils, fire reduced C that was free from minerals by 41% (-4.4 MgC ha-1 ) but not C associated with minerals, and only in depths ≤ 5 cm. Fire also transformed the properties of remaining mineral soil organic matter by increasing the proportion of C in a pyrogenic form (from 3.2% to 7.5%) and associated with minerals (from 47% to 58%), suggesting the remaining soil C is more resistant to decomposition. Laboratory assays illustrated that fire reduced microbial CO2 respiration rates by 59% and the activity of eight extracellular enzymes that degrade cellulosic and aromatic compounds by 40-65%. Lower decomposition was correlated with lower inorganic N (-49%), especially ammonium, suggesting N availability is coupled with decomposition. The relative increase in forms of soil organic matter that are resistant to decay or stabilized onto mineral surfaces, and the associated decline in decomposition suggest that low-intensity fire can potentially promote mineral soil C storage in pools with long mean residence times in coniferous forests.

  View details for DOI 10.1111/gcb.15648

  View details for PubMedID 33884700

• Quantifying Methane Emissions from Natural Gas Water Heaters. Environmental science & technology Lebel, E. D., Lu, H. S., Speizer, S. A., Finnegan, C. J., Jackson, R. B. 2020

  Abstract

  Methane emissions from natural gas appliances remain the least characterized portion of the fossil-fuel supply chain. Here we examine water heaters from 64 northern California homes to (1) quantify methane emissions from natural gas leaks and incomplete combustion while off, turning on or off, and in steady-state operation from 35 homes; and (2) characterize daily usage patterns over 1-2 months per water heater to estimate activity factors from 46 homes. Individual tankless water heaters emitted 2390 [95% CI: 2250, 2540] g CH4 yr-1 on average, 0.93% [0.87%, 0.99%] of their natural gas consumed, primarily from on/off pulses. Storage water heaters emitted 1400 [1240, 1560] g CH4 yr-1 on average, 0.39% [0.34%, 0.43%] of their natural gas consumption. Despite higher methane emissions, tankless water heaters generate 29% less CO2e20 than storage water heaters because they use less energy to heat a unit of water. Scaling our measured emissions by the number of storage and tankless water heaters in the United States (56.8 and 1.2 million, respectively), water heaters overall emitted an estimated 82.3 [73.2, 91.5] Gg CH4 yr-1, 0.40% [0.35%, 0.44%] of all natural gas consumed by these appliances, comparable in percentage to the EPA's estimate of methane emissions from upstream natural gas production.

  View details for DOI 10.1021/acs.est.9b07189

  View details for PubMedID 32250600