While many of us have seen articles linking tobacco smoke to ADHD, most of us have not been thinking about air pollution as a relevant clinical factor. Air pollution is a leading cause of health problems globally, and it is also linked to psychiatric problems in children and adolescents.

Understanding the problem
Air pollution refers to the mix of harmful particulate matter, gas, and vapor in the air. It can be categorized by setting (indoor vs outdoor; rural vs urban), source (man-made vs natural), and toxicity. Harmful gases include ozone, nitrous, and sulfur gases (collectively referred to as smog) produced by vehicle exhaust, industrial emissions, and the burning of carbon fuel. Particulate matter (PM) refers to microscopic solids and liquids. Various forms of PM can be released into the air from roads and construction sites, as well as solid products formed from chemical reactions in the atmosphere. Smaller particles are more harmful given their propensity to enter deeper airways and trigger inflammation.

Air quality is also impacted by local climate and geography. Patients who live or attend schools near highways or in cities may be impacted by automobile pollutants. Mountains can trap pollution over a city (eg, Los Angeles, Salt Lake City, and Mexico City). Arid climates and drought worsen air quality. Forest fires are a major source of air pollution—soot and ash are smaller particles that disperse widely.

Chief indoor culprits of air pollution are cigarette smoke, carbon monoxide, household products, pesticides, carbon monoxide, mold, and building materials such as asbestos.

How air pollution affects our patients
Compared to adults, children have a less developed respiratory epithelium, are more likely to get respiratory infections, often spend more time outdoors, and may be less concerned about hygiene. Once exposed to potential pollutants, the body mounts an inflammatory response, including cytokines IL-1 β, IL-6, and TNF α. These inflammatory mediators can be neurotoxic and affect several areas of the brain, including the prefrontal cortex and the hippocampus (­Brockmeyer S and D’Angiulli A, Transl Neurosci 2016;7(1):24–30).

A recent study from California showed that teens exposed to more fine particulate matter (PM2.5, or particles with a diameter of 2.5 microns or less) had higher levels of autonomic reactivity (a physiologic marker for anxiety) and higher self-reported levels of anxiety and depression (Miller J et al, Psychosom Med 2019;81(7):641–648). Likewise, a British longitudinal study demonstrated associations between air pollution exposure at age 12 and depression and conduct problems by age 18 (Roberts S et al, Psychiatry Res 2019;272:8–17). There is also emerging evidence around climate change or eco-anxiety occurring in kids and adolescents.

Researchers suggest a link between increased exposure to air pollution and decreased global IQ and psychomotor development, plus increased utilization of special education services in males. CNS damage may occur through various mechanisms: neuroinflammation, oxidative stress, glial activation, and white matter injury. Drawing specific conclusions is difficult due to heterogeneity of studies. For instance, some studies included exposure to indoor air pollution, including secondhand smoke. Furthermore, it is not clear if there is a critical period where exposure to air pollution is more detrimental to the child (Suades-Gonzalez E et al, Endocrinology 2015;156(10):3473–3482).

Still, asthma is common, linked to air pollution, and associated with a host of mental health problems, including internalizing problems. A 2019 study reported that air pollution is responsible for up to 33% of incident asthma cases (Khreis H et al, Eur Respir J 2019;54(4):1802194). The connection between asthma and psychiatric disorders seems bidirectional: Youth with asthma may become more vigilant of their health, confuse breathing difficulties with symptoms of anxiety or anxiety attacks, or be more stressed by increased demands for self-care (Pateraki E et al, J Clin Psychol Med Settings 2018; 25(1):20–31). Some inhaler formulations may also have side effects that mimic the symptoms of anxiety. Conversely, psychiatric comorbidity correlates with poorer asthma control and increased ER visits (Richardson L et al, 2006; Pediatrics 2006;118(3):1042-1051). Although asthma symptom burden is associated with worse anxiety and depression symptoms, the good news is that treating mental health seems to improve asthma control, although the literature does not explicitly establish this connection.

Secondhand smoke exposure increases asthma prevalence and severity, and predicts a child’s tobacco use (Farber H et al, Pediatrics 2015;136(5):e1439–e1467). Other challenges include the long-term risks of cancer in people exposed to secondhand smoke, and the risk of house fires.

Addressing air pollution in clinical practice
There are many things we can do to help our patients in this space.

Assessment
Inquire about wheezing or shortness of breath, especially when a patient describes paroxysmal anxiety symptoms or problems during aerobic exercise. It is important to think about other modifiable risk factors for asthma, including adolescent smoking, vaping, and possible exposure to secondhand smoke by peers or family members. Communicate with the child’s primary provider, who can order pulmonary function tests and refer to a pulmonologist if necessary. For patients with known asthma, inquire about how asthma affects their mental health and support compliance with treatment.

Management
Address the impact of the child’s mental health condition on the child’s physical state (eg, depressed and/or not complying with medical treatment), as well as the impact of the environment on the child’s condition (eg, increased fatigue during a temperature inversion with reduced air quality).

Consider how children perceive the threat of air pollution. They may feel powerless and overwhelmed in the face of large-scale environmental problems. Fears of pollution may compound trauma in those affected by forest fires, for example. We also know that parental stress impacts a child’s functioning, and studies suggest that adults who perceive their air is unhealthy are more likely to report feeling ill, headaches, and respiratory symptoms, regardless of the actual air quality (Orru K et al, Int Arch Occup Environ Health 2018;91(5):581–589).

Explore children’s worries about air pollution, especially those living in communities impacted by temperature inversions and forest fires. Help them develop healthy, pro-social attitudes and behaviors about their environment.

Since parental anxiety exacerbates child anxiety and symptoms, address parents’ mental health care so they are more responsive to their children.

Education
Counsel parents who smoke to quit or smoke outdoors and provide motivational interviewing or referrals to additional support for those who are ambivalent.

The Environmental Protection Agency provides prevention, technology, measurement, and science information that can be helpful to families, such as an overview of the current air quality index data (www.epa.gov/technical-air-pollution-resources). The CDC provides links to air quality forecasts to help families and schools figure out which areas may have better air as well as protective measures to minimize ozone and wildfire smoke exposure (www.cdc.gov/air/default.htm). For families living near high-traffic areas or construction sites, encourage them to play and commute in areas with less exposure to pollutants, if possible. When appropriate, encourage families to take vacations in areas with better air quality. For patients who are especially vulnerable to air pollution, consider wearable sensor technology (Ryan PH et al, Sci Total Environ 2015;508:366–373). For indoor irritants and toxins such as allergens and smoke, some home furnace systems are said to scrub the air, and air purifiers may be helpful; electrostatic devices purport to pick up indoor particles, such as those blown in from regional fires. It is unknown how well these consumer products prevent respiration of particulate matter, so buyer beware.

CCPR Verdict: Current acute reductions in the use of polluting energy sources underline the impact of air pollution on our patients’ mental health. You won’t fix all the problems related to air pollution during a med check appointment, but we recommend routinely asking about indoor and outdoor sources of environmental pollutants and helping your patients and families minimize these exposures.