Health benefits to the pediatric population from reduction of ambient particulate matter in Krakow, Poland

There have been few assessments of the health benefits to children of policies aimed at curbing fossil fuel-related air pollution. This has resulted in a lack of awareness regarding their positive impact on the health of this vulnerable population. We estimated the pediatric health benefits of policies targeting coal burning in one of Europe’s most polluted cities, Kraków, Poland. We combined available data on child health outcomes, related concentration-response functions, childhood population counts, and concentrations of PM2.5 and PM10 based on city-wide air monitoring in Kraków. Two exposure reduction scenarios were examined. First, we used the observed decrease in air pollutant concentrations between 2010 and 2019. Second, we hypothesized a reduction to the annual World Health Organization (WHO) air quality guideline values issued in 2005. Between 2010 and 2019, the mean annual air pollution levels in Kraków decreased for both PM2.5 and PM10. Annual average PM2.5 concentrations declined by 39.1%, reaching 23.3 μg m−3; PM10 dropped by 39.2% to 34.6 μg m−3. These reductions in air pollution can be linked to numerous actions undertaken at local and national levels. We estimate that the forgone benefits in 2010 from not having achieved the PM levels observed in 2019 (on an annual basis) included: 505 (35.7%) fewer incident cases of asthma in the 1–14 age group, 81 fewer preterm births (16.8% decrease), 52 fewer cases of low birth weight (12.3% decrease), and 59 avoided asthma hospitalizations in 0–18 year olds. Compliance with the 2005 WHO PM2.5 guidelines in 2010 would have avoided 780 incident asthma cases in the 1–14 age group (54.5% decrease), 138 preterm births (28.3% decrease), and 90 cases of low birth weight (21.2% reduction) and 219 (54.2%) fewer asthma hospitalizations in 0–18 year olds. Large health benefits were also estimated for PM10 in both scenarios. This study estimated substantial health benefits for children in Kraków, which were largely attributable to clean air policies that restrict the use of coal and other solid fuels. Kraków provides a model for other cities in Europe and beyond that are affected by coal pollution and have high rates of preterm birth, low birth weight, and respiratory illness.


Introduction
Air pollution is the greatest environmental threat to health in Europe and globally [1,2] with fine particulate matter (PM 2.5 ) considered responsible for most health impacts.The largest anthropogenic source of air pollution is the burning of fossil fuels (coal, oil, and gas) for electricity generation, transport, industry, buildings, and households [3].Air pollution is a risk factor for stroke, heart attacks, chronic obstructive pulmonary disease, lung cancer, and premature death in adults, and is associated with many health effects in children.These include adverse birth outcomes, infant mortality, asthma exacerbation and incidence, other respiratory illness, delayed psychomotor development, reduced child intelligence, behavioral problems, and autism [4].
Fetuses, infants, and children are uniquely vulnerable to air pollution owing to a host of biological and behavioral factors, including the speed and complexity of development and the immaturity of the biological defense mechanisms for detoxifying chemicals, repairing DNA damage, and providing immune protection [5].Additionally, children often engage in vigorous outdoor activities, leading to higher exposure to air pollution and higher doses of pollutants reaching the lungs.
Despite improvements in ambient levels in many areas, air pollution has been identified by the World Health Organization (WHO) as a health priority in the sustainable development agenda [6].While the relative risk for air pollution is relatively low compared to other risk factors, it has a great impact on human health because of the very large number of people affected.Environmental policies aimed at tackling air pollution have proven to be effective, with substantial health benefits [7,8].
Kraków, the site of the present study, is the second largest and one of the oldest cities in Poland and is situated on the Vistula River in Malopolska Voivodeship.The population of the city in 2021 included over 780 000 citizens, with 120 000 children aged 1-14 yr [9].For many years, Kraków has been one of the most polluted Polish and European cities [10][11][12].Based on the estimates from ISGlobal-Ranking of Cities [13], Kraków has been classified in the 28th position (out of 858 European cities) for the highest mortality related to air pollution.Especially during the winter months, Kraków is often classified among the cities with the highest air pollution levels: for example, according to the IQAir live ranking, on January 12th, 2021, Kraków recorded the third worst air pollution in the world [14].The high levels of air pollution in Kraków have resulted largely from the burning of low-quality coal in residential stoves and, to a lesser extent, from emissions from traffic and power plants.Moreover, the city is surrounded by communes where poor-quality coal stoves continue to be the dominant home-heating system [11].
To address this problem, in the 1990s, the municipal government initiated actions to reduce air pollution in Kraków, including a co-financing program to help citizens replace old coal stoves and boilers with electricity or natural gas [15].However, for years, residential heating by coal has remained the major contributor to the very high levels of air pollution observed in Kraków, especially during the winter season [16].During the last 12 yr, efforts to reduce air pollution have intensified, largely due to citizen action campaigns, resulting in greater awareness of the population.
Here, we review the actions taken by the government, the citywide trend in air pollution levels, and the estimated benefits of the change in air quality for children's health.

Policies
The major policies were identified through a search of legal acts published by authorities at the level of Kraków City and the Małopolska region, as well as by a literature search [17].

Trends in air quality
Air pollution data were provided by the Chief Inspectorate for Environmental Protection openaccess database containing data from two measurement stations of the State Environmental Monitoring program since 2000 [18] that operated continuously between 2010-2019.The stations were located at Bujaka St. (Kurdwanów, southern part of the city, background station) and Bulwarowa St. (Nowa Huta, northeastern part of the city).
The air monitoring station at Bujaka St. was established to measure the background level of air pollution and it is located in the South part of the city in residential area with no significant sources of air pollution related to transport or industry.The second station-Bulwarowa St. is located in the North part of Krakow and was primarily established to measure air pollutants in the more industrial part of the Krakow.However, for the last two decades the main source of air pollution, the ironworks, almost stopped operation.In the supplementary material figure S1 shows the trends in air pollution levels at these two stations over the 2010-2019 period.The levels of air pollution were similar.Based on this data we assume that the average of the measurements taken in these two stations is representative for the city area.
Trends in air pollution levels over time were assessed by calculating the slope using a linear regression model.

Health benefits assessment
We estimated the health benefits in terms of avoided adverse birth outcomes, infant deaths, new cases of asthma, and hospital admissions due to asthma and upper respiratory infections related to changes in PM 2.5 and PM 10 levels in Kraków between 2010 and 2019.

Concentration-response (C-R) functions
We conducted a literature search to identify studies on the relationships between ambient air pollutants (PM 2.5 and PM 10 ) and selected health outcomes in the pediatric population (i.e.low birth weight, preterm birth, infant mortality, new cases of asthma, and hospital admissions due to respiratory tract diseases in children).These functions were derived from peerreviewed epidemiological studies and meta-analyses.
To choose the most relevant C-R functions, we prioritized studies conducted in more than one population, including at least one European or Polish population.
We calculated the beta coefficients shown in table 1 based on the natural log of the reported odds ratios.Because of the different study designs of the reference publications, we distinguished between C-R functions for short-term (daily exposure data) and long-term (annual exposure average level) exposure assessments.
The C-R functions were combined with demographic data, baseline incidence, and air pollution levels (2010 and 2019) for the Kraków population.Demographic data (age structure) of the Kraków population were provided by the Statistics Poland database [9].Daily data from the two air pollution monitors were averaged to determine the annual concentrations of pollutants [18].
Baseline incidence data (year 2010) were available for preterm births and low birth weight, as well as mortality, in the age group of 0-4 yr for the Kraków municipality from Statistics Poland databases [9].For asthma incidence data, we used the rate for Poland in 2010, based on the Global Burden of Disease estimates [25].The number of hospital admissions due to asthma and other respiratory diseases for Kraków was available from the National Health Fund (NHF), the branch for the Małopolska region.The NHF fulfills the function of a public payer in the Polish healthcare system: with funds from obligatory health insurance contributions, the fund finances and tracks the health services provided to the insured and reimburses medicines.For this analysis, asthma-related hospitalizations for the age group ⩽18 yr, as well as upper respiratory tract infections that required hospital admission (ICD-X codes J00-J06 and J30-J39) for children younger than 5 yr old, were included.

Health benefits estimation
The Environmental Benefits Mapping and Analysis Program (BenMAP) is a tool for estimating health impacts resulting from changes in ambient air pollution.BenMAP-Community Edition (BenMAP-CE) is an open source tool developed by the U.S. Environmental Protection Agency to assess the health benefits of improved air quality [26].In BenMAP-CE, the user enters data on air quality, area, study population, mortality or incidence rates, and dose-response functions.Based on the entered data and the selected scenario of air quality changes, the program determined the change in atmospheric air pollution and estimated the changes in the selected health effects resulting from this change.We have used log-linear model to estimate the potential benefits of air pollution reduction.
Equation of the function used in BenMAP-CE: where: ∆Y is the change in health effect (number of cases), Y_0 is the baseline incidence/mortality ratio, β is the coefficient from epidemiological studies, ∆PM is the change in the level of air pollution, Pop is the study population.
We estimated the impact of long-term exposure (i.e.average annual air pollutant concentration) to air pollution on low birth weight, preterm birth, asthma incidence, and infant mortality based on the reported associations.For hospital admissions, we estimated the impact of short-term exposure (i.e.24 h exposure on the day preceding the outcome).
Two different scenarios were used to assess the benefits for the pediatric population of Kraków.
Scenario 1 was based on the observed changes in air pollutant levels between 2010 and 2019.In this analysis, the number of cases avoided can be interpreted as the forgone benefits in 2010 from not having achieved the lower PM 2.5 levels observed in 2019.
Scenario 2 assumed a reduction in air pollution observed in 2010 to the levels recommended by the 2005 WHO guidelines for air quality [27]: for longterm (annual) exposure 10 µg m −3 for PM 2.5 and 20 µg m −3 for PM 10 , and for short-term (24 h) exposure 25 µg m −3 for PM 2.5 and 50 µg m −3 for PM 10 .The analysis was performed separately for PM 2.5 and PM 10 .BenMAP-CE calculates the estimated difference in pollution levels for the chosen scenario and the median number of avoided cases, together with the 95% confidence interval estimated using the Monte Carlo iteration method.
In addition to these two scenarios, we have estimated the avoided cases of low birth weight, preterm birth, asthma incidence and infant mortality had Krakow's air quality in 2019 met the WHO 2005 guidelines.

Air pollution policies
The major policies related to air pollution reduction are presented in table 2. It includes decisions at municipal, regional, and national levels.

Trends in air quality
Between 2010 and 2019, the mean annual air pollution levels in Kraków decreased for both PM 2.5 and PM 10 (figure 1).The annual average PM 2.5 concentrations declined by 39.1% from 38.1 µg m −3 in 2010 to 23.2 µg m −3 in 2019.PM 10 dropped from 56.9 µg m −3 in 2010 to 34.6 µg m −3 in 2019 (39.2% decline).
Despite the decline of air pollution levels, the PM 2.5 /PM 10 ratio was found to be in the range from 0.62 in year 2011 to 0.70 in 2013.This ratio indicates a major contribution of fine particles attributable to anthropogenic air pollution sources.The detailed information can be found in Supplementary material, (table S1).
In 2010, the annual air pollution concentrations exceeded the 2005 annual WHO guidelines [27] (10 µg m −3 for PM 2.5 and 20 µg m −3 for PM 10 ).Despite the fact that a total ban on burning coal, wood, and other solid fuels in boiler houses, stoves, and fireplaces was imposed in the city of Kraków on September 1st, 2019 [36], in 2019, the number of days when the daily air pollution levels exceeded the 24 h guidelines set by the WHO in 2005 was still very high: 103 d with PM 2.5 > 25 µg m −3 ; 62 d with PM 10 levels > 50 µg m −3 (figure 2).We have also observed that during the year 2020, the first year after the ban to use solid fuels entered into force, the number of days that exceeded the 24 h guidelines values was 94 for PM 2.5 and 56 for PM 10 .

Health estimates 3.3.1. PM 2.5
Based on the first scenario, i.e. with a 15.4 µg m −3 decline in the annual concentration of PM 2.5 , we estimated that 81 preterm births would have been avoided (16.8% of all preterm births observed in Kraków in 2010) and 52 (12.3%) cases of low birth weight would have been avoided if the mean annual level of air pollution in 2010 was as observed in 2019 (table 2).In the second scenario, a decrease in PM 2.5 levels to the WHO 2005 guideline annual mean value of 10 µg m −3 was estimated to avoid 28.3% of preterm births and 21.2% of low birth weight cases out of those reported in Kraków in 2010.
We also calculated the avoided number of incident cases of asthma (1-14 yr olds) related to the reduction in air pollution for both scenarios.We estimated a 35.7% reduction in incident asthma cases for the observed change in annual PM 2.5 between 2010 and 2019 and a 54.5% decrease if the 2010 PM 2.5 level was lowered to the WHO 2005 guidelines.In addition, we estimated two avoided deaths in the age group 0-4 yr (a decrease of 5.0% in the 2010 incidence) for the observed reduction in annual PM 2.5 from 2010 to 2019, and three fewer deaths (a decrease of 8.9% in the 2010 incidence) had PM 2.5 , which was reduced to the annual WHO 2005 limit.
With respect to the observed decrease in daily PM 2.5 to the 2019 level, we estimated 16 fewer hospitalizations due to upper respiratory diseases in the age group of 0-4 yr (2.4% of the total in 2010) and 59 avoided cases of asthma hospitalizations in the age group of 0-18 yr, corresponding to 11.6% of the total in 2010.
In the second scenario, assuming that the annual PM 2.5 level in 2010 was at the 2005 WHO guideline value (10 µg m −3 ), we estimated 780 fewer new cases of asthma in 1-14 yr olds (54.5% reduction), 138 avoided preterm births (28.3% reduction), and 90 (21.2%) fewer cases of low birth weight.Had there been compliance with the WHO daily guidelines, we estimated that there would have been 219 (54.2%) fewer asthma hospitalizations in 0-18 yr olds and 37 (5.7%) fewer respiratory hospitalizations among 0-4 yr olds (5.7% reduction).Detailed data are presented in tables 3 and 4.

PM 10
We also estimated a substantial number of avoided cases in relation to the PM 10 changes.We estimated that the reduction of PM 10 levels in 2010 to  [34] defining the rules for targeted subsidies for the implementation of environmental tasks including: (1) permanent change of the solid fuel based heating system, consisting of: (a) connection to the district heating network, (b) installing gas heating, (c) installing electric heating, (d) installation of oil heating; (2) hot water connection due to decommissioning of fireplaces or fired boilers for solid fuels; (3) installation of solar collectors and heat pumps.

Subsidies:
(1) up to 100% of the costs incurred for complete applications submitted between 2014 and 2015; (2) up to 80% of the costs incurred for complete applications submitted in 2016; (3) up to 60% of the costs incurred for complete applications submitted in 2017; (4) up to 40% of the costs incurred for complete applications submitted in 2018 [33].
(Continued.)On 15 January 2016 the Małopolska Regional Assembly adopted a resolution prohibiting the use of solid fuels in the Kraków city and prohibiting burning coal and wood in boilers, stoves and fireplaces from 1 September 2019.Only gaseous fuels, oil, renewable energy sources and district heating will be allowed.Kraków became the first city in Poland to be covered by these rules [36].
23 January 2017 The anti-smog resolution for Małopolska Region As of 1 July 2017, the provisions of the anti-smog resolution for the Małopolska Region entered into force; and the ban on the burning of coal and coal fossils and biomass with a moisture content greater than 20% began [37].
24 April 2017 A transitional anti-smog resolution for the Małopolska Region adopted for Kraków The Małopolska Regional Assembly adopted a resolution dated 24 April 2017 on the introduction of bans concerning the scope of the operation of installations in which fuel burning takes place in the area of the Kraków municipality in the period from 1 July 2017 to 31 August 2019.As a result, from 1 July 2017, houses and flats in Kraków may not use: (1) fuels in which the mass fraction of hard coal or lignite of particle size 0-5 mm is greater than 5%, (2) fuels containing hard coal or lignite with at least one of the following parameters: calorific value below 26 MJ kg -1 , ash content greater than 10%, sulfur content greater than 0.8%, (3) fuels containing biomass with operational moisture content greater than 20%.The regulations would apply for about two years.On 1 September 2019, a total ban on coal burning in the area of the municipality of Kraków would come into force [38].

September 2017 National emission requirements for solid fuel boilers
The Regulation of the Minister of Development and Finance of 1 August 2017 on the requirements for solid fuel boilers, determines emission parameters for boilers placed on the market.This applies both to equipment authorized for sale and to the connection to the central heating system.This Regulation entered into force on 1 October 2017 [39].
those observed in 2019 would have resulted in 577 avoided incident asthma cases (39.5% reduction), two avoided deaths in 0-4 yr olds (5.3% decrease), and 61 (12.5%) avoided asthma hospitalizations (0-18 yr olds).Under the scenario in which PM 10 was reduced to the WHO 2005 guidelines, the number of incident asthma cases was lowered by 54.5%, deaths in 0-4 yr olds by 8.9% (three deaths), and asthma hospitalizations in 0-18 yr olds by 62.1% (see tables 3 and 4 for additional benefits and details).
In addition to the previous analysis, we have estimated the potential benefits that would have occurred had pollution levels observed in 2019 been reduced to meet the WHO 2015 guidelines (for the long-term effects only).The expected reduction in number of cases is as high as a 30.6% in asthma incident cases for PM 2.5 and 27.4% for PM 10 .In addition, achieving the WHO 2005 guidelines in 2019 would have resulted in a 14.1% lower number of preterm births and 10.2% fewer cases of low birth weight (table 5).

Discussion
This study is unique in that it assesses the health benefits to children of policy-related reductions in air pollution in Poland.There have been several attempts to assess the effect of air pollution on human health for the Polish population [11,[42][43][44][45] but only one study in the pediatric population (0-6 yr) [11].
We previously reported a significant improvement in air quality based on personal air monitoring in our Kraków cohort study of pregnant women and their children based on personal air monitoring [17].The present analysis of city-wide air monitoring data shows a similar reduction of PM 2.5 as well  as PM 10 levels over a recent 10 yr period in Kraków, consistent with prior reports [15,43].Improved air quality can be attributed in large part to major policy changes that reduce air pollution from solid fuel combustion, most importantly the phase-out and eventual ban of coal and other solid fuel for heating purposes.However, despite the reduction of levels of particulate matter, the PM 2.5 /PM 10 ratio is still relatively high indicating that the anthropogenic sources are still the major source of air pollution.
We observed significant decreases between 2010 and 2019 in both the annual average air pollutant concentrations and the number of days with pollution levels above the then-current WHO guidelines.The reduction in air pollution was associated with substantial benefits for children's health, with the largest estimated numbers and percent reductions of avoided cases being for preterm births (28.3%), low birth weight (21.2%), asthma hospitalizations (54.2%), and asthma incidence (54.5%) among children and   A substantial number of avoidable upper respiratory tract infections were also estimated.The estimated number of avoided incident cases of asthma estimated in our study is much higher than the average effect (11.5% reduction) found for 18 European countries [46] when assuming a reduction in air pollution level to the annual limit of the WHO 2005 guidelines.However, the average annual PM 2.5 level for the countries included in the analysis (11.6 µg m −3 ) was considerably lower than that in Kraków.In another study by Khreis et al [47] in Bradford, England, it was estimated that 27% of incident asthma cases (0-18 yr) could be attributed to PM 2.5 air pollution and 33% of asthma incidence could be attributed to PM 10 air pollution (any level).In their study, reduction of PM 2.5 to the WHO 2005 annual standard of 10 µg m −3 was linked with a 1.6% decrease in incident asthma cases and a reduction in annual PM 10 to 20 µg m −3 with two avoided cases (0.1%), which are far smaller benefits than we observed in the present analysis; however, the annual level of air pollution estimated in Bradford for PM 2.5 was higher on average by only 1 µg m −3 compared to the WHO 2005 standard.The reference level chosen in this analysis was based on the guidelines in force for the years considered in this analysis.However, we note that in September 2021, new more stringent Guidelines for Air Quality were published by the WHO: annual average, 5 µg m −3 for PM 2.5 , 15 µg m −3 for PM 10 , 24 h average, 15 µg m −3 for PM 2.5 ; 45 µg m −3 for PM 10 [40,41,48].This report underestimates the true impact of improved air quality in Kraków.In this analysis, only a few outcomes were considered: those for which reliable data on dose-response functions were available from studies that included at least one European.For example, only cases of morbidity requiring hospital admissions were considered, omitting ER visits and illnesses not requiring medical intervention [49].For the analysis of the short-term effects we used the hospitalization data based on the NHF records, which are public payer data.There may be some underestimation of the total number of hospital admissions because of this.However, in Poland there is a very limited number of hospitalizations not reimbursed by NHF due to obligatory health insurance for all workers (including those who are self-employed, run a business, etc) and their families.Even private hospitals have a contracts with NHF which is paying for hospitalizations.For the analysis of asthma incident cases we have used incidence estimates from the Global Burden of Disease for Poland, not Krakowspecific ones.One can assume that the true asthma incidence in Krakow is higher than those countrywide: a study conducted in different Polish regions showed that the prevalence of asthma in the age groups 6-7 yr and 13-14 yr in Krakow population is one of the highest among populations included [50].Furthermore, owing to the lack of available data, our analysis did not include ultrafine particles; however, a recent meta-analysis revealed that this fraction of PM increased the number of asthma exacerbations, subsequent emergency room visits, and hospital admissions in children [51].Finally, neurodevelopmental, cognitive, and behavioral effects associated with PM were not included in the analysis.However, even the present limited analysis demonstrates the large potential benefits related to the observed reduction in air pollution.

Conclusion
This study estimated substantial health benefits to children in Kraków starting in utero, that were attributable to clean air policies restricting the use of coal and other solid fuels.Kraków can provide a model for other cities in Europe and elsewhere that are affected by coal pollution and have high rates of preterm birth, low birth weight, and respiratory illness.

A Pac et alFigure 1 .
Figure 1.Mean annual levels of ambient PM2.5 and PM10 in Kraków from 2010 to 2019 (the corresponding slopes for regression lines are: −2.4 per year for PM10 and −1.7 per year for PM2.5).
with air pollution > 2005 WHO guidelines only, Daily background assumed: 2.4 µg

Table 1 .
The concentration-response functions (per 10 µg m −3 increase) used in this study.

Table 2 .
[28,29]or policies related to the air pollution reduction program in Kraków.City guards together with the inspectors of the Department of Environmental Management of the City of Kraków started to check on waste incineration in solid fuel stoves used for heating[28,29].
[32]t resolution to enact a ban on the use of solid fuels for heating in Kraków from 2018[32].Repealed by the Regional Administrative Court in Kraków(22 August 2014), judgment maintained by the Supreme Administrative Court (September 2015).

Table 2 .
[35]tinued.)Solid fuel boilers shall meet the requirements set out in the Commission Regulation (EU) 2015/1189 of 28 April 2015 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for solid fuel boilers from 1 January 2020[35].

Table 3 .
Benefits to child health from reductions in PM2.5 and PM10-long-term effects (impact of mean annual air pollution level on health outcomes).

Table 4 .
Benefits to child health (avoided cases) from reductions in PM2.5 and PM10-short-term effects (impact of mean daily air pollution level on health outcome).

Table 5 .
Long-term (impact of mean annual air pollution level on health outcomes) benefits to child health from reductions in PM2.5 and PM10 observed in 2019 to 10 µg m −3 for PM2.5 and 20 µg m −3 for PM10 (2005 WHO guidelines).