New research from the University of Minnesota School of Public Health and Colorado State University shows that breathing dirty air – even for just a day – likely causes people to become more aggressive and violent.
Their findings were recently published in the journal Epidemiology.
The researchers examined the association between daily violent and non-violent crimes and short-term increases in air pollution across 301 counties in 34 states during a 14-year period.
Data for the study was gathered from the FBI’s National Incident-based Reporting System and the Environmental Protection Agency’s Air Quality System. Daily pollution levels were determined based on the amount of fine particulate matter – such as diesel exhaust chemicals—and ozone in the air.
The study found:
- increases in daily air pollution levels raised the risk of violent criminal behavior, such as assaults;
- air pollution did not increase the risk of non-violent crime, which are crimes that do not involve force, threats or injury (e.g., property theft);
- the risk of violent behavior increased even at low pollution concentrations that are usually considered safe for people to breathe;
- results were consistent across different community types, including regions with different socioeconomic status, racial diversity and age. In other words, it is not the community driving this relationship.
“While our study cannot identify the exact processes that link air pollution and violent behavior, we believe that exposure to air pollution has immediate effects on the brain, which results in behavioral changes,” said study lead author and Assistant Professor Jesse Berman.
These effects may increase the impulsivity of people and escalate what is known as their “fight or flight” stress response.
Everyday minor conflicts, such as an argument with a neighbor, may become quickly heated and result in more serious physical altercations.
“Our findings have important implications for public health practitioners and policy makers,” said Berman. “If we know that an area is going to have increased air pollution, it might make violent behavior more likely.
This information can be relayed to police officers and other first responders so that they can prepare. Likewise, if increased violent crimes result in injuries, hospitals and paramedics could be advised as well.”
Berman is continuing to examine the influence of other environmental factors on crime rates with upcoming research looking into how air temperatures relate to the commission of violent offenses.
Air pollution is of serious concern across the globe, and is fueled by rapid population growth, continuous urbanization, increases in industrialization, continuous rises in energy demand, deforestation, and increases in car density, especially in major cities [1, 2]
Various anthropogenic activities lead to atmospheric degradation, such as emissions from vehicles, especially those that are older or poorly maintained; coal-powered industrial activities; construction, which produces dust; foundries and smelters; tobacco use; combustion that produces enormous heat; metal-based industries; mining; and excessive pesticide and chemical use [3–7].
This bleak scenario is further worsened through poor environmental management and regulation, use of inefficient technologies (with low production and high environmental deterioration), construction of congested roads, and the inability to strictly implement environmental regulations and laws, as well as a lack of awareness among the population about the serious health and psychological outcomes of pollution.
This issue is even more prominent in underdeveloped and developing countries, where it is a serious concern as it adversely affects public health, alters the quality of life, and impacts the economy (by affecting agricultural production, for example) [8, 9].
Atmospheric heavy metals (lead, mercury, copper, zinc, cobalt, nickel, and cadmium), SO2, CO, NO2, benzene, particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and chlorofluorocarbons (CFCs), are the primary contributors to air pollution [7, 10–12].
The presence of these pollutants at levels beyond permissible limits causes serious health issues, such as breathing problems, allergies, cancers, cardiovascular and respiratory diseases, and even mortality [12, 13]. Elders, infants, toddlers, children, sensitive people, and those suffering from asthma and such other disorders are more vulnerable (physically and psychologically) to the effects of air pollution [14, 15].
The World Bank  has provided an excellent updated insight of the fertility rate for all countries around the world, based on total births per woman, which could be linked to global warming/greenhouse gases and air pollution [17, 20, 21].
Kihal-Talantikite et al.  extensively reviewed the adverse impacts of proximity to polluted areas on the outcomes of pregnancy, such as infant mortality, premature birth, low birth weight, congenital malformation, intrauterine growth retardation, and gestational age. The physical effects associated with air pollution are widely studied, reported, and reviewed [23–28].
Industrial power plants, vehicle emissions, fossil fuels, and biomass combustion have been identified as major sources of PM, which acts as a primary pollutant and a secondary product of different gases, including NH3, NOx, and SO2 [12, 27, 34, 35].
Time-series studies have assessed the association between daily mortality and ambient air pollution in different western countries [29, 37–39], and different major Chinese cities, including Hong Kong , Wuhan , Guangzhou , Shanghai , and Beijing .
Approximately 800 million people were affected by the hazardous dense haze (covering an area of 1.4 million km2) in January 2013, which generated serious concern about air pollution among the residents of Eastern China [15, 42]. Yang et al.  reported that 1.2–2 million deaths per annum in China are attributed to air pollution, which was the fourth most prominent cause of disability-adjusted lifespans. Lu et al.  reported that rapid industrial, urbanization, and population growth are major sources of China’s continuously-deteriorating air quality, and are posing a significant threat to public health. Approximately 65–75% of industrial powerhouses in China are still coal-operated (i.e., coal is a major fuel source), and are designated as major pollution sources [6, 44].
Owing to the current situation, air reporting systems have been developed and installed in 190 cities (945 sites) across China. This system reports air quality on an hourly basis, focusing on six air pollutants: PM2.5 (PM<2.5 μm), PM10 (PM<10 μm), SO2, NO2, O3, and CO. Estimating and understanding outdoor air pollutants and their burden on public health would help to control air pollution [13, 43].
Air pollution is one of the leading factors that upsets human emotions and alters behavior [45, 46]. Long-term exposure to polluted air results in a variety of psychological problems (such as stress, depression, anxiety, irritation, becoming short-tempered, and mood swings), which adversely affect behavior (such as eating, recreation, commuting, traveling, and socialization) [13, 23, 47, 48].
A recent study indicated that older people and females were suffered more and were more anxious because of low air quality than younger people and males . Various studies have demonstrated the positive impacts of clean air on the human psyche, resulting in a pleasant mood and positive behavior .
Similarly, different studies have revealed a positive correlation between increased criminality (aggressive and violent behaviors) in humans and elevated temperatures (specifically in the summer) and air pollution [51–53]
. Air pollution has also been correlated with depression, a serious mental disorder affecting people globally, which is continuously increasing . Depression is characterized by a loss of pleasure and interests, guilt, sadness, inter alia, decrease in libido, disruption to sleep, and a loss of concentration . There are several studies available that show a positive correlation between air pollution and depressive disorders that adversely affect human behavior [55–57].
Air pollution-associated mortalities [27, 32]; and age-, gender-, and season-dependent adverse impacts/effects of air pollution on humans [58–60] are well documented, but most of these studies focused on physical factors. Therefore, an effort was made to study the effects of air pollution on both the physical and psychological health of Chinese students using a detailed questionnaire, and the first two portions were dedicated to each physical and psychological health.
The study included a total of 2048 subjects, who were recruited from 54 universities and schools across China. The largest number of individuals was recruited from Nanjing (21.2%), followed by Beijing (12.5%) and Changsha (11.2%). It was ensured that participants from different age groups were included. Of the total respondents, 47.3% were 16–25 years old. The study considered both genders; 55.2% of the subjects were female, while 44.8% were male. Table 1 presents the demographics of the respondents that took part in this study. Table 2 shows the average of air quality pollutants for the sampled cities. Table B in S2 File shows the interquartile ranges for the air pollutants across the samples cities (Oct 2015—March 2016).
The first section of the questionnaire covered the adverse impacts of air pollution on the physical health of the recruited subjects. Of the total respondents, 88.9% reported that they have felt (always, often, and some of the time) the ill effects of air pollution, suggesting that air pollution is a major public health concern across China. The subjects suffered from different effects at varying magnitudes; 25.0% often suffered from sneezing, a dry throat, and eye irritation, and 34.0% occasionally experiences these effects. Of the total respondents, 62.0% had suffered (always, often, and sometimes) breathing problems and have faced respiratory problems. Fewer people suffered from coughing/wheezing and headaches/dizziness than those that have suffered from other ENT (ear, nose, and throat) problems. In total, 9.1%, 10.5%, and 24.6% of the respondents always, often, and sometimes felt that they had lower energy levels in response to air pollution, respectively. For sleeping patterns, 8.7%, 11.5%, and 23.4% of the respondents always, often, and sometimes faced problems in their sleeping patterns, respectively. Table 3 shows the reported physical health effects caused by air pollution, while Tables Tables44 and and55 contain gender- and city-, and age-dependent responses, respectively.
The next section of the questionnaire was focused on the behavioral and psychological impacts of air pollution. In total, 62.1%, 78.1%, and 65.5% of the respondents suffered from depression/sadness/unpleasant moods, reduced exercise routines/jogging speed/jogging duration, and reduced walking speed, respectively, due to air pollution. A total of 1136 (55.4%) respondents reported that they feel anxiety and frustrated during hazy days. Of the total respondents, 44.1% reported that they become aggressive due to haze/air pollution, and a higher number reported that they exhibit more aggressive behaviors during warmer days (63.9%) than they do during colder days (27.6%). Table 6 shows the behavioral effects of air pollution noted by the respondents, while Tables C and D in S2 File show the reported gender- and city-dependent, and age-dependent effects, respectively.
The third section of the questionnaire contained questions about the preventive measures adopted by the respondents. Of the total respondents, 68.2% reported that they use a mask to cover their noses and mouths, 22.0% used eyeglasses/goggles to protect their eyes, 63.2% drink more water to help them flush out toxins (absorbed through the lungs/skin), and 65.2% indicated that they have a rich diet (high levels of vitamins C and E, and Omega-3-Fatty acids) to improve their immune response. Table 7 shows the practices adopted by the respondents to prevent the adverse impacts of air pollution, while Tables E and F in S2 File show the gender- and city-, and age-dependent practices, respectively.
The final section of the questionnaire evaluated the recruited individuals’ awareness levels and perception of pollution. Of the total subjects, 96.0% reported that smoking should be banned in public areas and restricted to designated zones, 69.3% were aware that air pollution causes cardiovascular diseases and respiratory problems, such as lung cancer, and that air pollution was one of the major causes of mortality in China over the last two decades. Regarding industrialization, 68.8% of the respondents did not agree with compromising their health because of environmental and air pollution originating from China’s development, economic strength, and GDP growth from industrialization. Of the total subjects, 91.9% were aware of major pollutants, such as CO, SO2, and NO2. Vehicle exhausts (27.8%), industrial emissions (27.8%), and coal burning (21.4%) were identified as major sources of air pollution (Fig 2). Television (20.8%), cell phones (20.6%), and the internet (20.5%) were the leading sources of information about air pollution and its adverse health effects (Fig 3). Table 8 shows the respondents’ levels of awareness and perception of air pollution and its associated health risks, while Tables G and H in S2 File show the gender- and city-, and age- dependent knowledge and perceptions of air pollution, respectively.
More information: Jesse D Berman et al. Acute air pollution exposure and the risk of violent behavior in the United States, Epidemiology (2019). DOI: 10.1097/EDE.0000000000001085
Journal information: Epidemiology
Provided by University of Minnesota