Reference
Wong CM, Tsang H, Lai HK, et al. Cancer mortality risks from long-term exposure to ambient fine particle. Cancer Epidemiol Biomarkers Prev. 2016;25(5):839-845.
Design
Longitudinal outcome study
Participants
This study recruited and followed 66,820 adults (aged 65 or older) through one of the 18 Elderly Health Centers in Hong Kong. The volunteers were recruited between 1998 and 2001 and then followed until 2011. This sampling represented approximately 9% of total Hong Kong residents of this age group.
Study Parameters Assessed
All Hong Kong residents have a unique identity card number; this number, linked to death records, was used to track the participants’ vital status and cause of death.
Primary Outcome Measures
Investigators tracked the cause of death for all of the participants throughout the study period, specifically documenting deaths due to cancer.
Data from hourly monitoring at fixed-site sampling stations was used to estimate the annual concentration of fine particulate matter (PM2.5) (defined as particles that are less than 2.5 μm in diameter) in residential areas. Using this data, regression models calculated the concentration of PM2.5 at different heights above sea level. These models were used to estimate the mean concentration of PM2.5 for each residential location using floor numbers to estimate the vertical height of each address (people in Hong Kong usually live in high-rise buildings).
Key Findings
In this study cancer mortality rose in relation to long-term exposure to increasing levels of PM2.5. For every 10 μg/m3 increase of PM2.5, the risk of dying from breast cancer increased by 80%; female genital cancer by 73%; cancers in the upper digestive tract by 42%; and cancers in accessory digestive organs (liver, bile ducts, gall bladder and pancreas) by 35%. All increases in cause-specific mortality showed statistical significance. Overall, cancer mortality risk increased 22% for every 10 μg/m3 increase in exposure to PM2.5. The mean PM2.5 exposure was 33.7 μg/m3.
In short, poor air quality has been clearly linked to all of the most common pressing chronic health problems in our modern society.
Practice Implications
Urban air is highly polluted and has long been associated with cardiovascular and respiratory morbidity and mortality. The literature is replete with articles from major cities around the globe consistently showing that cardiovascular and respiratory deaths increase soon after a spike in urban air pollutant levels.1-2 Along with increased mortality, hospital admission for cardiovascular and respiratory issues also increase.3-4 Air pollutants have also been shown to increase the rates and severity of atopic conditions, infertility, diabetes, obesity, and even autism, along with declines in cognitive functioning.5-10 In short, poor air quality has been clearly linked to all of the most common pressing chronic health problems in our modern society.
Particulate matter from vehicular exhaust is consistently found to be more damaging to human health, with smaller particles causing the most damage, than particulate matter from combustion of non-petroleum sources.11 These smaller particles find their way into virtually all cells in the body where they cause a great deal of oxidative damage.12-13
As mentioned above, multiple studies have repeatedly shown that acute exposures to urban air pollutants are followed by increased mortality rates (primarily cardiovascular and respiratory). This study has now documented that chronic exposure to PM2.5 increased mortality from various cancers. With cardiovascular disease, cancer, and respiratory diseases accounting for the vast majority of deaths, preventive medicine physicians should recognize the necessity of reducing exposure to these ubiquitous toxicants.
Multiple studies have repeatedly shown that acute exposures to urban air pollutants are followed by increased mortality rates.
With all the standard and social media reports on the horribly elevated levels of air pollution in China, it might be easy to dismiss this study as an outlier that would not apply to most clinical practices in North America. However, there are urban areas within the United States that have been found to have PM2.5 levels that reach the average levels found in this study (33.7 μg/m3) (find data for your city and many other cities around the globe at http://aqicn.org). Further, current research has not clearly shown what the threshold level of PM2.5 exposure is for increased rates of cancer mortality from chronic exposure.
Over the last 10 years, my review of the literature on the adverse health effects of air pollution resulted in a major change in my recommendations to patients who wish to have as much vitality in their lives as possible. For years my best health recommendations would include getting off sugar and white flour, reducing or eliminating red meats, eating organic as much as possible (especially for the Environmental Working Group’s Dirty Dozen™), exercising, meditating, and taking a small number of necessary supplements. My primary recommendation now? Invest in a high-quality air purifier for your bedroom.
