Nathan Glen Phillips, Robert C. Ackley, Andee Krasner

We surveyed 197 Massachusetts and Rhode Island houses ranging in building style and age to test whether homes served by fracked gas have higher indoor methane concentrations ([CH4]) than in homes without gas. The answer is clearly “Yes”. From basements and single-floor slab homes to third floors of triple deckers, indoor [CH4] in households with gas service was significantly elevated over outdoor [CH4], averaging 1.48 parts per million (ppm) elevation over outdoor ambient [CH4] (p < 0.0001 - 0.0068), and up to 38.2 ppm above outdoor ambient [CH4]. Ninety-three percent of houses with gas showed higher indoor [CH4] than the average [CH4] in non-gas houses. As in other parts of the fracked gas supply chain where a few “super-emitter” leaks account for a disproportionately large percent of total emissions, the distribution of indoor [CH4] was skewed, with a smaller proportion of houses showing much larger [CH4] than the average household [CH4] elevation. For example, the 20% of the houses with highest indoor [CH4] averaged a [CH4] of 8.4 ppm, more than quadruple outdoor ambient [CH4]. By contrast, indoor [CH4] in gas-free homes was not significantly different from outdoor conditions (p > 0.05), except marginally on the first floor (0.10 ppm elevation; p = 0.029), less than 1/10th the average first floor [CH4] elevation in homes served with gas. In 88% of homes investigated, the source of leaks from fracked gas pipes or appliances could be confirmed. There was no relationship between indoor [CH4] and house age or square footage; residents should not assume that newer homes are less prone to indoor gas leaks. This result provides statistical and direct evidence that fracked gas leaks and exposure is not only commonplace, but likely in New England homes served by gas within the housing types studied. While we did not assess health impacts, leaks of any size are of concern because leaks do not tend to decrease over time and also constitute a condition of chronic exposure. A national program testing for indoor methane concentrations would broaden understanding of how widespread and persistent the pattern observed in this study is, including in low income and rental households.