Impact of choice of inhalers for asthma care on global carbon footprint and societal costs: a long-term economic evaluation

Figures & data

Figure 1. Global DPI market shares across scenarios. Abbreviations. DPI, dry powder inhaler; PU, pack units; SU, standard dose units

Table 1. Global CO₂e emissions, costs, and DALYs across status quo scenario and scenarios of DPI market share increases (2020–2070) – Central value of social cost of carbon.

	Scenario A	Scenario B	Scenario C
Global GHG Emissions (tonnes)
Total GHG emissions due to inhaler use	826,085,119	513,123,982	346,040,335
DPI emissions	21,324,352	33,195,736	42,656,808
MDI emissions	804,760,767	479,928,246	303,383,527
Global Costs (in 2020 USD)^a
Total costs	$165,157,875,274	$177,266,421,583	$192,471,416,054
Costs due to inhaler use^b	$136,500,105,936	$158,829,332,352	$179,519,282,113
DPI costs	$74,975,403,621	$105,805,989,986	$134,067,144,592
MDI costs	$61,524,702,315	$53,023,342,366	$45,452,137,521
Social cost of carbon^c	$28,657,769,338	$18,437,089,231	$12,952,133,941
Global DALYs^d
Total DALYs due to GHG emissions	73,848 − 228,928	49,371 − 153,051	36,045 − 111,740
Per capita costs (in 2020 USD)^e
Per patient costs (inhaler costs + SCC)	$7.82	$8.38	$9.07

Abbreviations. CO2e, carbon dioxide equivalent emissions; DALY, disability adjusted life-year; DPI: dry powder inhaler; IPCC, Intergovernmental Panel on Climate Change; MDI, metered dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs and DALYs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the central estimate of the 3% discounted social cost of carbon published by the United States government. ^dThe range for DALYs was calculated using the damage factors estimated by Tang et al. for the A1B and A2 IPCC scenarios. ^ePer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 2. Differences in global CO₂e emissions, costs, and DALYs across status quo scenario and scenarios of DPI market share increase (2020–2070) – Central value of social cost of carbon.

	Scenario B vs. A		Scenario C vs. A
	Absolute difference	Percent change (%)	Absolute difference	Percent change (%)
Global CO2e Emissions (tonnes)
Total CO2e emissions due to inhaler use	−312,961,137	−37.9	−480,044,784	−58.1
DPI emissions	11,871,384	55.7	21,332,456	100.0
MDI emissions	−324,832,521	−40.4	−501,377,240	−62.3
Global costs (in 2020 USD)^a
Total costs	$12,108,546,309	7.3	$27,313,540,780	16.5
Costs due to inhaler use^b	$22,329,226,416	16.4	$43,019,176,178	31.5
DPI costs	$30,830,586,365	41.1	$59,091,740,971	78.8
MDI costs	−$8,501,359,948	−13.8	−$16,072,564,794	−26.1
Social cost of carbon^c	−$10,220,680,108	−35.7	−$15,705,635,398	−54.8
Global DALYs^d
Total DALYs due to CO2e emissions	−24,476 to −75,877	−33.1	−37,803 to −117,188	−51.2
Per capita costs (in 2020 USD)^e
Per patient costs (inhaler costs + SCC)^f	$0.6	7.2	$1.2	15.9

Abbreviations. CO2e, carbon dioxide equivalent emissions; DALY, disability adjusted life-year; DPI, dry powder inhaler; IPCC, Intergovernmental Panel on Climate Change; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate; ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the central estimate of the social cost of carbon at the 3% discount rate estimated by the United States government. ^dDALYs were discounted at a 3% annual rate. ^eDALYs were calculated using the damage factors estimated by Tang et al. for the IPCC A2 scenario. ^fPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 3. Global CO₂e emissions, costs, and DALYs across status quo scenario and scenarios of DPI market share increases (2020–2030) – Central value of social cost of carbon.

	Scenario A	Scenario B	Scenario C
Global GHG emissions (metric tons CO2e)
Total GHG emissions due to inhaler use	97,166,103	85,386,456	73,879,754
DPI emissions	2,604,484	3,046,830	3,523,704
MDI emissions	94,561,619	82,339,626	70,356,050
Global Costs (in 2020 USD)^a
Total costs	$106,649,826,396	$114,675,235,303	$122,936,280,406
Costs due to inhaler use^b	$101,949,335,672	$110,534,683,064	$119,343,220,483
DPI costs	$56,678,310,048	$68,509,596,103	$80,531,783,615
MDI costs	$45,271,025,625	$42,025,086,961	$38,811,436,868
Social cost of carbon^c	$4,700,490,724	$4,140,552,240	$3,593,059,924
Global DALYs^a
Total DALYs due to GHG emissions^d	16,656 − 51,633	14,746 − 45,712	12,875 − 39,913
Per capita costs (in 2020 USD)^e
Per patient costs (inhaler costs + SCC)	$26	$27	$29

Abbreviations. CO2e, carbon dioxide equivalent emissions; DALY, disability adjusted life-year; DPI, dry powder inhaler; GHG, greenhouse gas; IPCC, Intergovernmental Panel on Climate Change; MDI, metered dose inhaler; SCC, social cost of carbon; USD, United States dollars.

Notes: ^aGlobal costs and DALYs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the central estimate of the 3% discounted social cost of carbon published by the United States government. ^dThe range for DALYs was calculated using the damage factors estimated by Tang et al. for the A1B and A2 IPCC scenarios. ^ePer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 4. Differences in global CO₂e emissions, costs, and DALYs across status quo scenario and scenarios of DPI market share increase (2020–2030) – Central value of social cost of carbon.

	Scenario B vs. A		Scenario C vs. A
	Absolute difference	Percent change (%)	Absolute difference	Percent change (%)
Global CO2e Emissions (tonnes)
Total CO2e emissions due to inhaler use	−11,779,648	−12.1	−23,286,349	−24.0
DPI emissions	442,346	17.0	919,220	35.3
MDI emissions	−12,221,994	−12.9	−24,205,569	−25.6
Global Costs (in 2020 USD)^a
Total costs	$8,025,408,907	7.5	$16,286,454,010	15.3
Costs due to inhaler use^b	$8,585,347,392	8.4	$17,393,884,810	17.1
DPI costs	$11,831,286,055	20.9	$23,853,473,567	42.1
MDI costs	−$3,245,938,664	−7.2	−$6,459,588,757	−14.3
Social cost of carbon^c	−$559,38,484	−11.9	−$1,107,430,800	−23.6
Global DALYs^d
Total DALYs due to CO2e emissions^e	−1,910 to −5,921	−11.5	−3,781 to −11,720	−22.7
Per capita costs (in 2020 USD)^f
Per patient costs (inhaler costs + SCC)	$2	7.3	$4	14.8

Abbreviations. CO2e, carbon dioxide equivalent emissions; DALY, disability adjusted life-year; DPI, dry powder inhaler; IPCC, Intergovernmental Panel on Climate Change; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the central estimate of the social cost of carbon at the 3% discount rate estimated by the United States government. ^dDALYs were discounted at a 3% annual rate. ^eDALYs were calculated using the damage factors estimated by Tang et al. for the IPCC A2 scenario. ^fPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Figure 2. Global costs across status quo scenario and scenarios of DPI market share increase (2020–2070). Abbreviations. DPI, dry powder inhaler; MDI, metered dose inhaler; SCC, social cost of carbon; USD, United States dollars.

Figure 3. Global costs across status quo scenario and scenarios of DPI market share increase (2020-2030). Abbreviations. DPI, dry powder inhaler; MDI, metered dose inhaler; SCC, social cost of carbon; USD, United States dollars.

Table 5. Global CO₂e costs between the status quo scenario and scenarios of DPI market share increase (2020–2070) – High-impact social cost of carbon.

	Scenario A	Scenario B	Scenario C
Global costs (in 2020 USD)^a
Total costs	$225,232,670,908	$215,718,915,083	$219,332,799,123
Costs due to inhaler use^b	$136,500,105,936	$158,829,332,352	$179,519,282,113
DPI costs	$74,975,403,621	$105,805,989,986	$134,067,144,592
MDI costs	$61,524,702,315	$53,023,342,366	$45,452,137,521
Social cost of carbon^c	$88,732,564,972	$56,889,582,732	$39,813,517,009
Per capita costs (in 2020 USD)^d
Per patient costs (inhaler costs + SCC)	$10.3	$10.0	$10.2

Abbreviations. CO2e, carbon dioxide equivalent emissions; DPI, dry powder inhaler; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the 95th percentile of the social cost of carbon at the 3% discount rate estimated by the United States government. This 95th percentile value represents higher-than-expected impacts from temperature change. ^dPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 6. Differences in global CO₂e costs across status quo scenario and scenarios of DPI market share increase (2020–2070) – High-impact social cost of carbon.

	Scenario B vs. A		Scenario C vs. A
	Absolute difference	Percent change (%)	Absolute difference	Percent change (%)
Global costs (in 2020 USD)^a
Total costs	−$9,513,755,824	−4.2	−$5,889,871,785	−2.6
Costs due to inhaler use^b	$22,329,226,416	16.4	$43,019,176,178	31.5
DPI costs	$30,830,586,365	41.1	$59,091,740,971	78.8
MDI costs	−$8,501,359,948	−13.8	−$16,072,564,794	−26.1
Social cost of carbon^c	−$31,842,982,240	−35.9	−$48,919,047,963	−55.1
Per capita costs (in 2020 USD)^d
Per patient costs (inhaler costs + SCC)	−$0.3	−2.7	−$0.1	−0.5

Abbreviations. CO₂e, carbon dioxide equivalent emissions; DPI, dry powder inhaler; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the 95th percentile of the social cost of carbon at the 3% discount rate estimated by the United States government. This 95th percentile value represents higher-than-expected impacts from temperature change. ^dPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 7. Global CO₂e costs between the status quo scenario and scenarios of DPI market share increase (2020–2030) – High-impact social cost of carbon.

	Scenario A	Scenario B	Scenario C
Global costs (in 2020 USD)^a
Total costs	$116,066,666,092	$122,968,202,920	$130,130,541,826
Costs due to inhaler use^b	$101,949,335,672	$110,534,683,064	$119,343,220,483
DPI costs	$56,678,310,048	$68,509,596,103	$80,531,783,615
MDI costs	$45,271,025,625	$42,025,086,961	$38,811,436,868
Social cost of carbon^c	$14,117,330,420	$12,433,519,857	$10,787,321,344
Per capita costs (in 2020 USD)^d
Per patient costs (inhaler costs + SCC)	$28	$29	$31

Abbreviations. CO2e, carbon dioxide equivalent emissions; DPI, dry powder inhaler; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the 95th percentile of the social cost of carbon at the 3% discount rate estimated by the United States government. This 95th percentile value represents higher-than-expected impacts from temperature change. ^dPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.

Table 8. Differences in global CO₂e costs across status quo scenario and scenarios of DPI market share increase (2020–2030) – High-impact social cost of carbon.

	Scenario B vs. A		Scenario C vs. A
	Absolute difference	Percent change (%)	Absolute difference	Percent change (%)
Global Costs (in 2020 USD)^a
Total costs	$6,901,536,828	5.9	$14,063,875,734	12.1
Costs due to inhaler use^b	$8,585,347,392	8.4	$17,393,884,810	17.1
DPI costs	$11,831,286,055	20.9	$23,853,476,567	42.1
MDI costs	−$3,245,938,664	−7.2	−$6,459,588,757	−14.3
Social cost of carbon^c	−$1,683,810,563	−11.9	−$3,330,009,076	−23.6
Per capita costs (in 2020 USD)^d
Per patient costs (inhaler cost + SCC)	$2	5.8	$3	11.8

Abbreviations. CO₂e, carbon dioxide equivalent emissions; DPI, dry powder inhaler; MDI, metered-dose inhaler; USD, United States dollars.

Notes: ^aGlobal costs were discounted at a 3% annual rate. ^bInhaler costs were subject to generic entry considerations. It was assumed that inhaler costs undergo a 50% reduction at year 2030, and a 90% reduction for all subsequent years. ^cThe social cost of carbon was calculated using the 95th percentile of the social cost of carbon at the 3% discount rate estimated by the United States government. This 95th percentile value represents higher-than-expected impacts from temperature change. ^dPer capita costs were calculated by dividing global costs with the asthma population estimates derived using total population and urbanization estimates from the United Nations and asthma prevalence rates from the Global Burden of Disease study.