A Better Way to Compare Aircraft Noise and Emissions?
by Nick Miller

The World Health Organization (WHO) has recently published “Burden of disease from environmental noise, Quantification of healthy life years lost in Europe.” The title sparked my interest because there is an on-going effort in the U.S. to quantify and compare the relative adverse effects on society caused by aviation noise and aviation produced air pollutants. For the primary air pollutants, current U.S. work translates benefits of reductions to such things as reductions in premature mortality and in chronic bronchitis, to which dollar benefits are assigned. For noise, the Noise Depreciation Index (NDI) reveals how many dollars in housing prices are gained by reducing noise.

I’ve always been troubled by this comparison of dollars of house price saved versus dollars of lives saved –not because I doubt either the calculations or assigning dollars to a life, which is standard in many cost benefit analyses. But my opinion, shared I think by many who deal with community reactions to aircraft noise, is that house prices really don’t reflect the adverse noise effects of living near a busy airport. For one thing, realtors and sellers go out of their way to down-play the aircraft noise issue.

Well, whether or not we want to pursue that debate, here come the Europeans and WHO, with “disability-adjusted life-years” (DALYs) as a method for quantifying any environmental health effect, and a report specifically addressing noise. Though my hopes for enlightenment about aircraft noise were immediately dashed when I learned that this report deals almost exclusively with the effects of road traffic noise, the DALY method may eventually have some use for comparison of aviation noise and emissions effects.

So how do we compute DALYs? Basically it’s the sum of years of life lost (e.g., premature mortality) and years lived with disability, or years of healthy life lost (e.g., suffering chronic bronchitis). The noise produced disabilities the WHO report examines are cardiovascular disease, cognitive impairment in children, sleep disturbance, tinnitus and annoyance. These are all adverse health effects consistent with the WHO definition of health as being “a state of complete physical, mental and social well-being.”

Computation of DALYs requires knowledge of the number of people exposed to each level of noise, a dose-response relationship that gives percent of people affected at each level, the “disability weight,” DW, assigned to the effect (DW equals zero means no health effect, DW equals one, you die), and the number of years of living with the disability or years of life lost. Obviously, many assumptions are required, but I like the way the large number of assembled subject area experts synthesized their knowledge and the research literature results to quantify each variable and calculate the DALYs for each health effect.

What most struck me, was the number of experts (41 are listed) who participated in developing the report. In contrast, current U.S. efforts have required that many people come up to speed on the effects of aircraft noise on people, working with an additional very few who had actually worked in the field of aircraft noise effects. (Three cheers to the FAA for bringing in experts from outside the U.S. to assist with development of the Aviation Noise Impacts Roadmap.) To be clear, those who had to learn, were already experts, many in acoustics, just not in aviation noise and its effects.

In some ways, how sad. In the 1970’s the U.S. lead the world in developing the knowledge needed to formulate a national policy on noise and noise control. But those efforts all stopped short in the early 1980’s. Hence, most of those with expertise have retired and no new blood added for these three decades.

Now that we are concerned about how we can expand the U.S. air transport system, change airspace use, add runways, and increase the use of under-utilized airports, recognition has come that we better understand what the noise and air quality effects will be on society. Let’s hope that we can develop enough understanding to provide the aviation decision-makers with the information they need for science based noise and emissions policy. Perhaps a bit more of looking to research results gathered outside the U.S. would benefit our efforts.