Small particles associated with lower respiratory tract infections

Relation

Horne BD, Joy EA, Hofmann MG, et al. Short-term increase in air pollution due to particulate matter and acute lower respiratory tract infection [published online ahead of print April 13, 2018].Am J Respir Crit Care Med.

Objective

To understand the connection between small fine dust particles (PM_2.5) levels and medical encounters for acute lower respiratory tract infections (ALRI) in very young children, with a secondary aim to find the same associations for older children, adolescents and adults.

Draft

Observational case crossover design

Participant

The study included more than 146,000 people of all ages and genders living in a narrow strip of urban/suburban land in north-central Utah known as the Wasatch Front. The area experiences large variability in PM_2.5Concentrations due to periodic temperature inversions during winter and is home to more than 80% of Utah's population.

Inclusion criteria were based on diagnosis of acute lower respiratory tract infection (ALRI) during the study period (1999-2016). The majority (77%) of participants were children aged 0 to 2 years.

Study parameters assessed

Particulate matter concentrations were measured between 1999 and 2016 using community-based air quality monitors.

Primary outcome measures

Short-term periods of PM_2.5Increases were matched to the timing of the increase in reported encounters based on physician visits for ALRI. The population was grouped according to age groups (0–2, 2–17, and ≥18 years). After stratification by age group, odds ratios (ORs) for ALRI were calculated based on healthcare contacts.

Key insights

Short-term exposure to elevated PM_2.5Air pollution has been associated with greater health care utilization for ALRI among young children, older children, and adults.

ALRI encounters in young children increased within a week of elevated PM levels_2.5, with another peak after 3 weeks. The 28-day cumulative OR was 1.15 per 10 μg/m³Increase in PM_2.5(95% confidence interval [CI]: 1.12-1.19). Similar increased odds of ALRI were observed in older children.

Short-term exposure to elevated PM_2.5Air pollution has been associated with greater health care utilization for ALRI among young children, older children, and adults.

There was also an increase in diagnosed and laboratory-confirmed respiratory syncytial virus (RSV) (particularly in young children) and influenza-related encounters (particularly in older children and adults) following elevated ambient PM levels_2.5levels.

Practice implications

Lead investigator Dr. Horne while speculating about the connection between PM_2.5and ALRI, said the following: "Air pollution itself can make the human body more susceptible to infections or impair the body's ability to fight off the infectious agents. It may be that PM_2.5causes damage to the respiratory system so that a virus can successfully cause an infection or this PM_2.5impairs the immune response, causing the body to develop a less effective response to fight off the infection.”¹

There are many naturopathic methods to support immune function in children and adults, including a lifelong habit of eating a healthy, whole food-based, phytochemical-rich diet. Several studies indicate that exposure to air pollution results in increased oxidative stress and that dietary supplementation may play a modulating role in the acute effects of air pollutants. For example, one study suggests that B vitamins may reduce the unwanted effects of particulate matter in the air in some people. Other nutrients such as vitamin C, vitamin E, vitamin D and omega-3 polyunsaturated fatty acids (PUFAs) have shown protective effects against the damage caused by particulate matter in air polluted environments.²and antioxidant-rich, colorful fruits and vegetables have improved resistance to asthma.³

Lung diseases such as asthma can be aggravated or triggered by particulate matter in the air. Observational studies suggest that those who consume omega-3 PUFAs are less likely to develop asthma. Preclinical studies confirm this observation and show that omega-3 PUFAs protect against asthma triggers, including viruses⁴and allergens.⁵However, there are no intervention studies that have examined the effect of omega-3 fatty acids on asthma exacerbation risk.⁶It should be noted that supplementation with omega-3 PUFAs alone may increase susceptibility to oxidative damage.⁷For this reason, supplementation with omega-3 PUFAs in combination with antioxidants is warranted.

In addition to the direct effects of fine dust on the lungs, there may be other explanations to explain the connection between increased levels of fine dust in the air and lung infections. According to Horne, lung damage caused by air pollution "could lead to longer periods of ALRI symptoms or more severe symptoms requiring more intensive medical care for the infected person. Periods of acute increases in PM may also occur_2.5lead to people spending more time indoors where they are in closer contact with others who carry infectious agents and can spread the infection to them.”¹

Extending these thoughts, more time indoors may also contribute to inadequate vitamin D production by reducing sun exposure. Reduced vitamin D status can also be exacerbated by air pollution itself, which can block ultraviolet (UV) radiation from entering the atmosphere, resulting in a similar net effect of low vitamin D status.⁸A recent intervention study of vitamin D in asthma found that the rate of first exacerbation was reduced in subjects who showed an increase in circulating vitamin D after supplementation.⁹suggesting the potential of vitamin D to protect against air pollution-induced exacerbations.

Prevention of ALRI and relief of symptoms can be achieved by alerting the public to an acute increase in PM concentrations_2.5. When this occurs, people may be able to prevent infections or reduce the severity or duration of ALRI symptoms by reducing their exposure to air pollution.¹⁰For example, people can be warned to be more vigilant and not to touch their face without washing their hands first, and to engage in other preventive behaviors known to reduce the risk of infection.¹

The potential health and economic benefits of establishing nonpharmacological approaches (e.g., reduced exposure, hygiene considerations, nutritional supplementation) to disease management are enormous. Further studies are needed to determine how different combinations of nutrients can minimize the impact of airborne particles, particularly particulate matter_2.5on various aspects of lung health.