Long-term dynamics of death rates of emphysema, asthma, and pneumonia and improving air quality

Figures & data

Table 1 Measurements of air pollutants used in the study, 1993–2010

Air pollutant	Number of monitored sites	Number of month-specific measurements
Ozone	69	148
Nitrogen dioxide	15	180
Sulfur dioxide	35	180
Carbon monoxide	41	180
PM10	68	180
PM2.5	60	132

Abbreviation: PM, particulate matter.

Figure 1 Levels of six air pollutants in North Carolina, 1993–2011. Individual pollutants were placed onto a single graph by utilizing arbitrary units to enable a collective visualization of the trends.

Abbreviation: PM, particulate matter.

Figure 2 Seasonal fluctuations of air-pollutant levels: summer (red, 3 months) and winter (blue, 3 months), 1993–2011.

Abbreviation: PM, particulate matter.

Table 2 Demographic characteristics of North Carolina population with cause-specific respiratory mortality, 1993–2010

Demographic characteristic	Cause of death
	Emphysema	Asthma	Pneumonia
Number of deaths	13,187	5,509	10,1374
Sex, n
Males	7,951 (60.3%)	1,806 (32.8%)	48,517 (47.9%)
Females	5,236 (39.7%)	3,703 (67.2%)	52,857 (52.1%)
Race, n
Caucasians	11,866 (90.0%)	3,567 (64.8%)	82,759 (81.6%)
African-Americans	1,237 (9.4%)	1,853 (33.6%)	17,665 (17.4%)
Other	84 (0.6%)	89 (1.6%)	950 (1.0%)
Age, n
<15 years old	7 (0.1%)	103 (1.9%)	595 (0.6%)
15–39 years old	40 (0.3%)	429 (7.8%)	1,633 (1.6%)
40–64 years old	2,504 (19.0%)	1,723 (31.3%)	12,054 (11.9%)
65+ years old	10,636 (80.7%)	3,254 (59.1%)	87,091 (85.9%)

Figure 3 Trends in death rates for emphysema, asthma, and pneumonia in North Carolina, 1983–2010. Mortality rates were age-adjusted to the 2000 North Carolina population.

Table 3 Associations between trends in emphysema, asthma, and pneumonia death rates and dynamics of air pollutants in North Carolina, 1992–2010

Potential health-impact factor	Emphysema	Asthma	Pneumonia
Ozone, ppb	0.0061±0.0030, P<0.05	0.0082±0.0056*	−0.0011±0.0019*
Smoking	0.0493±0.0056†, P<0.0001	0.0649±0.0105†, P<0.0001	0.0413±0.0034†, P<0.0001
SO2, ppb	0.0547±0.0106†, P<0.0001	0.0598±0.0173†, P<0.001	0.0309±0.0093†, P<0.001
Smoking	0.0399±0.0074†, P<0.0001	0.0563±0.0121†, P<0.0001	0.0360±0.0063†, P<0.0001
NO2, ppb	0.0153±0.0062, P<0.01	0.0270±0.0094, P<0.005	0.0030±0.0053*
Smoking	0.0456±0.0090†, P<0.0001	0.0511±0.0140†, P<0.001	0.0455±0.0076†, P<0.0001
CO, ppb	0.0004±0.0001†, P<0.0001	0.0006±0.0001†, P<0.0001	0.0001±0.0001*
Smoking	0.0300±0.0083†, P<0.001	0.0349±0.0129, P<0.01	0.0388±0.0074†, P<0.0001
PM2.5, μg/m^3	0.0155±0.0066, P<0.05	0.0116±0.0083*	0.0044±0.0063*
Smoking	0.0414±0.0072†, P<0.0001	0.0329±0.0093†, P<0.001	0.0462±0.0067†, P<0.0001
PM10, μg/m^3	0.0045±0.0039*	0.0204±0.0058†, P<0.001	−0.0015±0.0035*
Smoking	0.0583±0.0069†, P<0.0001	0.0644±0.0109†, P<0.0001	0.0499±0.0057†, P<0.0001

Notes: For each air pollutant, the effect of smoking was evaluated. The effects of month-to-month fluctuations in disease-specific mortality for emphysema, asthma, and pneumonia are not shown in the table, but they also were evaluated for each month.

* P>0.05;

† significant under Bonferroni correction for multiple comparisons.

Abbreviation: PM, particulate matter.

Table 4 Timeline of key federal and North Carolina state-specific air regulations and actions

Year	Acts and regulations	Federal or North Carolina acts and regulations	Description of the act or regulation	Pollutant(s) under regulation	Level of targeted pollutant in North Carolina at the time of act/regulation (as shown in Figure 1)
1970	Congress passes the Clean Air Act, which called for the first tailpipe-emission standards	Federal	The new standards go into effect in 1975 with NOx standard for cars and light-duty trucks of 3.1 g/mile (gpm)	NOx	NA
1977–1988	Tightened emission standards in the Clean Air Act	Federal	For cars, in 1977–1979 the NOx standard became 2.0 gpm; in 1981, it was reduced to 1.0 gpm For light-duty trucks, in 1979 the standard became 2.3 gpm; in 1988, the standard became 1.2 gpm For heavier trucks, in 1988 the standard became 1.7 gpm	NOx	NA
1990–1994	Tier 1 tailpipe standards	Federal	For cars, the NO standard reduced from 1.0 gpm to 0.6 gpm For light-duty trucks, the standard ranged from 0.6 to 1.53 gpm, depending on truck’s weight	NOx	↑ NO2 level
1990–1998	National Heavy Duty Truck Engine Standards	Federal	NO rate drops from 6.0 g/bhp-h to 4.0 g/bhp-h for both diesel and gasoline heavy-duty vehicles PM rate lowered from 0.6 to 0.1 g/bhp-h for diesel	NOx, PM	↑ NO2 level ↓PM10 level
1994	EPA issued new standards for chemical plants to reduce toxic air pollutants	Federal	To reduce the emission of toxic air pollutants* at or near industrial locations by more than 0.5 million tons each year	188 toxic air pollutants to be regulated by EPA including dioxins, benzene, arsenic, beryllium, mercury, and vinyl chloride	NA
1995	EPA launches an incentive-based acid-rain program, Phase 1	Federal	To reduce SO2 and NOx emissions, ie, 2 million-ton reduction in NOx emissions and reduction of SO2 emissions by 40% below their required level Under regulation were 110 mostly coal-burning electric utility plants located in 21 Eastern and Midwestern states	SO2, NOx	↑ NO2 level ↑ SO2 level
1998	EPA promulgates the NOx State Implementation Plan (SIP) Call	Federal	To identify the states in which the NOx emissions from certain sectors were significantly contributing to nonattainment in or interfering with maintenance in downwind states	NOx	↑ NO2 level
1999–2001	National Low Emission Vehicles (NLEV) Program	Federal	To reach a 50% reduction in NOx emissions from light-duty vehicles and 17% for light-duty trucks	NOx	↑ NO2 level
2000	EPA launches an incentive-based acid-rain program, Phase II	Federal	To reduce SO2 and NOx emissions	SO2, NOx	↑ NO2 level ↓ SO2 level
2001	NC EMC adopted rules to reduce ozone-forming NO emissions from coal-fired power plants and other large industrial sources	North Carolina	To reduce NOx by 68% between 2000 and 2006	NOx	↓ NO2 level
2002	Clear Skies Initiative and alternative regulations	Federal	To reduce SO2 emissions by 70% and NOx emissions by 65% below current levels	SO2, NOx	↓ NO2 level ↑ SO2 level
2002	North Carolina General Assembly passed Session law 2002–4 (Senate Bill 1078), called Clean Smokestacks Act	North Carolina	To control multiple air pollutants from old coal-fired power plants; under the act, coal-fired power plants must achieve a 77% cut in NOx emissions by 2009 and a 73% cut in SO2 emissions by 2013. North Carolina’s two largest utility companies, Duke Power and Progress Energy, must achieve these emissions cuts through actual reductions at their 14 power plants in the state; requires Duke Energy to limit NOx emissions to 35,000 tons per year and Progress Energy to 25,000 tons per year for certain coal-fired units by 2007; to limit SO2 emissions to 150,000 tons per year and 100,000 tons per year from Duke Energy and Progress Energy, respectively, by 2009	NOx,SO2 The act does not set caps on mercury; however, when NOx and SO2 limits are met, it will also reduce mercury by about 60%–90%; also, that will lead to reduction of PM levels	↓ NO2 level ↑ SO2 level
2003	Clean Bus USA program	Federal	EPA provides funds for more than 4,000 school buses to be retrofitted to remove 200,000 pounds of particulate matter from the air over the next 10 years	PM	↓PM10 level ↓ PM2.5 level
2004	Tier 2 tailpipe standards	Federal	New emissions standards requiring cars, sport utility vehicles, minivans and light-duty trucks to be 77%–95% cleaner than in 1999; the new standard is 0.07 gpm for NOx; also, reduction in average SO2 levels to 30 ppm	SO2, NOx, CO	↓ NO2 level ↓ SO2 level ↓ CO level
2005	EPA issues the Clean Air Act Interstate Rule (CAIR)	Federal (for the eastern US)	To achieve the largest reduction in air pollution in more than a decade by permanently capping SO2 and NOx emissions	SO2, NOx	↓ NO2 level ↓ SO2 level
2006	North Carolina 1998 Clean Air Plan	North Carolina	Low sulfur gasoline requirements go in place statewide	SO2	↑ SO2 level
2007	Additional regulations in the Smokestacks Act	North Carolina	Requires Duke Energy to limit NOx emissions to 31,000 tons per year and Progress Energy to 25,000 tons per year for certain coal-fired units	NOx	↓ NO2 level
2007–2010	New heavy-duty engine standards	North Carolina	90%–95% lower emissions expected	CO	↓ CO level
2009	EPA approved North Carolina Clean Air Interstate Rules into the State Implementation Plan	North Carolina	NOx and SO2 emission allowances for North Carolina utilities to be lower than those set by the Clean Smokestacks Act	NOx, SO2	↓ NO2 level ↓ SO2 level
2009	Additional regulations in the Smokestacks Act	North Carolina	Requires Duke Energy to limit NOx emissions to 31,000 tons per year and Progress Energy to 25,000 tons per year for certain coal-fired units; the act also requires SO2 limits of 150,000 tons per year and 100,000 tons per year from Duke Energy and Progress Energy, respectively	NOx, SO2 Mercury, PM	↓ NO2 level ↓↓PM10 level ↑ PM2.5 level ↓ SO2 level
2011	North Carolina, the Tennessee Valley Authority (TVA), and several other parties agreed to a comprehensive settlement on the caps for all TVA coal-fired facilities	North Carolina and Tennessee	To decline annual basis to permanent levels of 110,000 tons of SO2 in 2019 and 52,000 tons of NOx in 2018; it requires TVA to install modern pollution controls or shutdown several of its coal-fired units	NOx, SO2	↓ NO, level ↓ SO2 level
2013	Additional regulations in the Smokestacks Act	North Carolina	Requires Duke Energy to limit SO2 emissions to 80,000 tons per year and Progress Energy to 50,000 tons per year for certain coal-fired units by 2013	SO2	NA

Notes: The acts and regulations that had a major impact on air quality in North Carolina are highlighted in gray. *Toxic air pollutants are those pollutants known or suspected to cause cancer or other serious health effects, such as birth defects or reproductive effects (http://www.epa.gov/airtrends/aqtrnd95/tap.html). Up and down arrows mean an increase or decrease of respective air pollutant level as compared with the years before the date of the act/regulation became effective.

Abbreviations: PM, particulate matter; NA, not applicable; EPA, Environmental Protection Agency; NC EMC, North Carolina Environmental Management Commission.

Table S1 Results of the sensitivity analysis

Potential health-impact factor	Emphysema	Asthma	Pneumonia
Ozone, ppb Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0056±0.0029, P>0.05	0.0052±0.0050, P>0.05	−0.0011±0.0019, P>0.05
	0.0433±0.0057, P<0.0001	0.0427±0.0097, P<0.0001	0.0411±0.0036, P<0.0001
Ozone, ppb Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0043±0.0069, P>0.05	−0.0004±0.0085, P>0.05	−0.0046±0.0024, P>0.05
	0.0777±0.0159, P<0.0001	0.1140±0.0205, P<0.0001	0.0403±0.0051, P<0.0001
Ozone, ppb Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	0.0092±0.0037, P<0.01	0.0004±0.0098, P>0.05	0.0052±0.0056, P>0.05
	0.0377±0.0066, P<0.0001	0.0104±0.0153, P>0.05	0.0241±0.0101, P<0.05
Ozone, ppb Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	0.0039±0.0031, P>0.05	−0.0003±0.0084, P>0.05	0.0054±0.0049, P>0.05
	0.0524±0.0056, P>0.0001	0.0682±0.0156, P<0.0001	0.0814±0.0097, P<0.0001
SO2, ppb Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0502±0.0108, P<0.0001	0.0289±0.0159, P>0.05	0.0331±0.0094, P<0.001
	0.0361±0.0075, P<0.0001	0.0375±0.0109, P<0.001	0.0379±0.0064, P<0.0001
SO2, ppb Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0551±0.0189, P<0.05	0.0535±0.0231, P<0.05	0.0027±0.0077, P>0.05
	0.0651±0.0145, P<0.0001	0.0978±0.0188, P<0.0001	0.0345±0.0052, P<0.0001
SO2, ppb Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	0.0823±0.0243, P<0.001	0.0298±0.0357, P>0.05	0.0596±0.0250, P<0.05
	0.0386±0.0167, P<0.0001	0.0432±0.0247, P>0.05	0.0194±0.0170, P>0.05
SO2, ppb Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	0.0358±0.0126, P<0.005	0.0387±0.0259, P>0.05	0.1094±0.0193, P<0.0001
	0.0471±0.0087, P<0.0001	0.0724±0.0180, P<0.0001	0.0666±0.0140, P<0.0001
NO2, ppb Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0159±0.0062, P<0.01	0.0281±0.0084, P<0.001	0.0029±0.0053, P>0.05
	0.0367±0.0094, P<0.0001	0.0179±0.0129, P>0.05	0.0469±0.0079, P<0.0001
NO2, ppb Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0434±0.0114, P<0.0001	0.0160±0.0163, P>0.05	0.0049±0.0051, P>0.05
	0.0410±0.0167, P<0.01	0.0987±0.0235, P<0.0001	0.0306±0.0067, P<0.0001
NO2, ppb Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	0.0135±0.0149, P>0.05	0.0224±0.0196, P>0.05	−0.01101±0.0145, P>0.05
	0.0621±0.0203, P<0.005	0.0352±0.0263, P>0.05	0.0591±0.0199, P<0.005
NO2, ppb Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	0.0024±0.0072, P>0.05	0.0385±0.0133, P<0.005	0.0098±0.0114, P>0.05
	0.0590±0.0104, P<0.0001	0.0477±0.0204, P<0.05	0.0986±0.0171, P<0.0001
CO, ppb Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0004±0.0001, P<0.0001	0.0002±0.0001, P>0.05	0.0002±0.0001, P<0.05
	0.0299±0.0084, P<0.001	0.0342±0.0120, P<0.01	0.0386±0.0073, P<0.0001
CO, ppb Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0013±0.0003, P<0.0001	0.0017±0.0004, P<0.0001	0.0002±0.0001, P>0.05
	0.0510±0.0149, P<0.001	0.0766±0.0179, P<0.0001	0.0298±0.0057, P<0.0001
CO, ppb Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	0.0005±0.0001, P<0.001	0.0007±0.0002, P<0.0001	0.0001±0.0002, P>0.05
	0.0267±0.0202, P>0.05	−0.0173±0.0258, P>0.05	0.0454±0.0211, P<0.05
CO, ppb Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	0.0001±0.0001, P>0.05	0.0008±0.0002, P<0.0001	0.0010±0.0001, P<0.0001
	0.0501±0.0101, P<0.0001	0.0334±0.0194, P>0.05	0.0352±0.0150, P<0.05
PM2.5, μg/m^3 Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0155±0.0066, P<0.05	0.0116±0.0083, P>0.05	0.0044±0.0063, P>0.05
	0.0414±0.0072, P<0.0001	0.0329±0.0093, P<0.001	0.0462±0.0067, P<0.0001
PM2.5, μg/m^3 Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0207±0.0113, P>0.05	0.0014±0.0105, P<0.05	0.0016±0.0045, P>0.05
	0.0578±0.0152, P<0.0001	0.0797±0.0141, P<0.0001	0.0352±0.0060, P<0.0001
PM2.5, μg/m^3 Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	0.0224±0.0168, P>0.05	0.0195±0.0186, P>0.05	0.0039±0.0214, P>0.05
	0.0498±0.0154, P<0.001	0.0049±0.0168, P>0.05	0.0446±0.0193, P<0.05
PM2.5, μg/m^3 Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	0.0030±0.0072, P>0.05	0.0030±0.0137, P>0.05	−0.0047±0.0101, P>0.05
	0.0560±0.0078, P<0.0001	0.0366±0.0154, P<0.05	0.0667±0.0106, P<0.0001
PM10, μg/m^3 Smoking	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)	Analysis 1 (ICD-9/10)
	0.0025±0.0039, P>0.05	0.0125±0.0053, P<0.05	−0.0012±0.0035, P>0.05
	0.0521±0.0072, P<0.0001	0.0395±0.0101, P<0.0001	0.0508±0.0059, P<0.0001
PM10, μg/m^3 Smoking	Analysis 2 (summer)	Analysis 2 (summer)	Analysis 2 (summer)
	0.0169±0.0071, P<0.05	0.0243±0.0083, P<0.05	−0.0029±0.0026, P>0.05
	0.0714±0.0142, P<0.0001	0.1020±0.0176, P<0.0001	0.0377±0.0050, P<0.0001
PM10, μg/m^3 Smoking	Analysis 3 (winter)	Analysis 3 (winter)	Analysis 3 (winter)
	−0.0104±0.0143, P>0.05	0.0407±0.0180, P<0.05	−0.0135±0.0143, P>0.05
	0.0828±0.0170, P<0.0001	0.0297±0.0213, P>0.05	0.0569±0.0162, P<0.0005
PM10, μg/m^3 Smoking	Analysis 4 (underlying)	Analysis 4 (underlying)	Analysis 4 (underlying)
	−0.0063±0.0047, P>0.05	0.0256±0.0084, P<0.005	0.0140±0.0074, P>0.05
	0.0662±0.0078, P<0.0001	0.0679±0.0163, P<0.0001	0.0993±0.0133, P<0.0001

Notes: The following factors were tested: the potential effect of International Classification of Diseases (ICD) code changes (from ICD-9 to ICD-10) (analysis 1), the effects of air pollutants on mortality during the summer (analysis 2) and winter (analysis 3), and the association when only underlying causes of death contributed to the cause-specific death rates (analysis 4).

Abbreviation: PM, particulate matter.