The health impacts are quantified in terms of premature mortalities. Epidemiological studies have

developed quantitative associations between increased human exposure to PM2.5 and increased risk

of premature death Specifically in this work, a 1% (range 0.4% -- 1.8%) increase in all-cause

mortalities for every 1 µg/m3 increase in the annually averaged PM2.5 exposure in the US is applied

for adults over the age of 30 years old [6].

This work quantifies the contribution to the aggregate PM2.5 health impacts of each emissions

species, time, location and sector. It must be noted that secondary organic aerosols are not captured

in this work.

Impacts of changing atmospheric composition on atmospheric response to emissions:

An adjoint sensitivity analysis of anthropogenic combustion emissions to PM2.5–related heath impacts

Irene C. Dedoussi, Steven R.H. Barrett Laboratory for Aviation and the Environment, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 33-115, Cambridge, MA 02139, USA

*NH3 in thousands of short tons

2000 2002 2004 2006 2008 2010 2012 2014

Year

7

8

9

10

11

12

Emission

s(×

103tons)

×104

CO

2000 2002 2004 2006 2008 2010 2012 2014

Year

0

0.5

1

1.5

2

2.5

Emission

s(×

103tons)

×104

NOx

PM2.5

SO2

NH3

*

References [1] Caiazzo, F., Ashok, A., Waitz, I. A., Yim, S. H. L., & Barrett, S. R. H. (2013). Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005. Atmospheric Environment, 79, 198–208. doi:10.1016/j.atmosenv.2013.05.081 [2] Dedoussi, I. C., & Barrett, S.R.H. (2014). Air pollution and early deaths in the United States. Part II: Attribution of PM2.5 exposure to emissions species, time, location and sector. Atmospheric Environment, 99, 610–617. [3] Dedoussi, I. C., & Barrett, S.R.H. (2015). US aviation air quality impacts and comparison with other sectors. Presentation given that Aircraft Noise and Emissions Reduction Symposium, September 22-25 2015, La Rochelle, France.. [4] Henze, D. K., Hakami, A., & Seinfeld, J. H. (2007). Development of the adjoint of GEOS-Chem. Atmospheric Chemistry and Physics, 7(9), 2413–2433. doi:10.5194/acp-7-2413-2007 [5] Holt, J., Selin, N.E., Solomon, S., 2015. Changes in inorganic fine particulate matter sensitivities to precursors due to large-scale us emissions reductions. Environmental Science and Technology 49, 4834–4841. doi:10.1021/acs.est.5b00008. [6] USA EPA, 2011. The Benefits and Costs of the Clean Air Act from 1990 to 2020. Technical Report March. Final report of U.S. Environmental Protection Agency; Office of Air and Radiation. URL: http://www.epa.gov/cleanairactbenefits/prospective2.html. [7] USA EPA, 2016. Air Pollutant Emissions Trends Data. URL: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.

*Sensitivities expressed in

ppl · µg/m3

kg/hr

*Sensitivities expressed in

ppl · µg/m3

kg/hr

Acknowledgements: Prof. Henze, Selin, and Solomon for discussions and to Katherine Travis for help with the NEI 2011 emissions in GEOS-Chem.

Sensitivity changes

We apply a long-term adjoint sensitivity analysis and calculate the four dimensional sensitivities (time

and space) of PM2.5 population exposure in the US with respect to each emissions species, using the

GEOS-Chem adjoint at 0.5° × 0.666° resolution over North America [4]. These sensitivities show how

the aggregate US population exposure is affected by a perturbation in the emissions (species, location,

time). We estimate the impacts of each sector by applying the 4D sensitivities to the 4D emissions of

each sector, as processed by the EPA National Emissions Inventory for 2005:

Introduction

Method

Air pollution and degraded air quality adversely impacts human health. Epidemiological studies link long-

term exposure to particulate matter PM2.5 (fine particulate matter, with an aerodynamic diameter less

than 2.5 µm; see schematic below) to an increased risk of premature mortality. Given it is the most

significant known cause for early deaths associated with outdoor air pollution, PM2.5 has been become

the predominant metric to quantify air quality.

Within the US, combustion emissions are the predominant source of ground level PM2.5

concentrations [6]. Air pollution impacts in the US have previously been estimated to be resulting in

200,000 premature mortalities every year for PM2.5 [1]. In an attempt to mitigate these impacts, it is

important to understand which emissions (species, location, time) are driving the impacts and how the

ongoing anthropogenic emissions changes affect the atmosphere’s response to emissions and

thereby this attribution of impacts to emissions. This poster summarizes work on the aforementioned

two objectives.

@J

@Ew

Ew,i,j,k@J

@Ew(i, j, k, t)

US aggregate PM2.5 exposure

origin of impacts (states)

time of emission

for each emissions species

= PM2.5 exposure attributable to

the sector

2005 impacts

Emissions changes

We use the adjoint sensitivities and attribute impacts to emissions from 7 sectors of economic activity

for 2005. The sectors include electric power generation, industrial activities, commercial/residential

activities and four modes of transportation (road, marine, rail, aviation). The emissions are based on the

EPA NEI 2005 dataset and the full-flight aviation AEDT dataset. The percentage contribution of each

sector to the aggregate US premature deaths is shown on the pie chart above [3].

The spatial origins of the PM2.5 annual health impacts are also traced back to the emissions that lead to

population exposure to PM2.5 using the GEOS-Chem adjoint sensitivities. On the plot on the right, we show

how much each state’s combustion emissions contribute to the aggregate annual PM2.5 health impacts.

The metric used is premature deaths. Given the cross-state pollution exchange, the state where the

impacts occur may not necessarily coincide with the state where the emissions occurred (which is what

is shown above).

Sensitivity to NOx emissions

The EPA reports significant emissions changes over the past 15 years in the US, as plotted above [7]. CO

emissions are reported to have decreased ∼15% between 2005 and 2011, NOx by ∼25% and SO2 by

∼55%. PM2.5 and NH3 remain approximately constant in domain aggregate numbers, but vary spatially in

the domain. It should be noted that these emissions reductions do not occur homogeneously in the

domain. For example, for SO2, the majority of which comes from power plants, the emissions reductions

(e.g. shutting down the power plant or installing scrubbers) are very localized, and heterogeneous over

the domain. In contrast NOx emissions, mostly from road transportation, are more uniformly decreasing

over the domain (e.g. due to technology improvements etc.).

These emissions reductions are likely to affect the atmospheric composition, and in particular the

atmosphere’s response to emissions (= adjoint sensitivity matrices). We assess how the changing

background atmospheric composition affects the values of the adjoint sensitivities, and thereby the

population exposure and health impacts of anthropogenic combustion emissions.

The figures below show near-surface level sensitivities (4 first layers of the grid, up to ∼500 m) of

PM2.5 population exposure in the US with respect to an emissions unit of NOx, and SO2. The

sensitivities are plotted for the year of 2006 and 2011, as well as the difference between the two

years (2011-2006). Given that the adjoint method is receptor-oriented, the plots show how a

perturbation in the corresponding emission in a location in the domain contributes to the aggregate

US population exposure to PM2.5. The shown changes in the sensitivities between the two years are driven by varying parameters

such as background emissions (and atmospheric composition), meteorology and population. The

difference in the meteorology between the two years is estimated to lead to ~5% of the changes.

Sensitivity to SO2 emissions

The sensitivity to NOx emissions has increased over land implying that the marginal benefit of a NOx

emissions reduction in 2011 is higher than 2006. This increased sensitivity of PM2.5 formation to

NOx emissions was also found by Holt et al. (2015).

We find that the sensitivity to SO2 emissions has primarily decreased, apart from areas near the

coasts.

Anthropogenic combustion emissions in the US in 2005 contributed to ~170,000 [77,000 – 300,000]

premature deaths [2]. In this section we assess the sources of the impacts in terms of sectors and in

terms of location.

Electric Power

Generation 24%

Industry 22% Commercial/

Residential 21%

Road 28%

Marine 4%

Rail 1%

Aviation 0.27% 0.3%