Unexpected potential protective associations between outdoor air pollution and cataracts

Abstract

Air pollution is one of the biggest public health issues, and the eye is continuously exposed to multiple outdoor air pollution. However, to date, no large-scale study has assessed the relationship between air pollutants and cataracts. We investigated associations between outdoor air pollution and cataracts in the Korean population. A population-based cross-sectional study was performed using data from the Korea National Health and Nutrition Examination Survey, including 18,622 adults more than 40 years of age. The presence of cataracts and their subtypes were evaluated by ophthalmologists. Air pollution data (levels of particulate matter, ozone, nitrogen dioxide, and sulfur dioxide) for the 2 years prior to the ocular examinations were collected from national monitoring stations. The associations of multiple air pollutants with cataracts were assessed by multivariate logistic regression analyses. Sociodemographic factors and previously known risk factors for cataracts were controlled as covariates (model 1 included sociodemographic factors, sun exposure, and behavioral factors, while model 2 further included clinical factors). Higher ozone concentrations were protectively associated with overall cataract which included all subtypes [single pollutant model: 0.003 ppm increase-model 1 (OR 0.89, p = 0.014), model 2 (OR 0.87, p = 0.011); multi-pollutant model: 0.003 ppm increase-model 1 (OR 0.80, p = 0.002), model 2 (OR 0.87, p = 0.002)]. Especially, higher ozone concentrations showed deeply protective association with nuclear cataract subtype [0.003 ppm increase-single pollutant model: model 2 (OR 0.84, p = 0.006), multi-pollutant model: model 2 (OR 0.73, p < 0.001)]. Higher tropospheric ozone concentrations showed protective associations with overall cataract and nuclear cataract subtype in the Korean population.

The Association of Ambient Air Pollution With Cataract Surgery in UK Biobank Participants: Prospective Cohort Study

“…Previous studies examining the association between exposure to air pollution and cataract have shown inconsistent findings and have been limited by their cross-sectional design, smaller sample size, and have only been examined in the Asian populations. 9 , 15 , 16 In a cross-sectional study of 5871 participants, a 1-SD increase in years of biomass fuel use was associated with a 28% increase in nuclear cataract for women in the Indian Eye Study, respectively. 16 In contrast, the KNHANES of 18,622 participants reported that higher ozone concentrations was associated with lower odds of cataract, whereas no significant association was identified between PM 10 and NO 2 with cataract.…”

“… 16 In contrast, the KNHANES of 18,622 participants reported that higher ozone concentrations was associated with lower odds of cataract, whereas no significant association was identified between PM 10 and NO 2 with cataract. 9 There has only been one longitudinal study that examined the relationship between ambient air pollution and cataract. 3 In a prospective Korean cohort (NHIS-NSC) of 115,728 participants, higher exposures to PM 10 , NO 2 , and SO 2 were associated with higher risk of cataract, whereas there was no significant association between PM 2.5 and incident cataract.…”

“…Studies examining the association between air pollution and cataract are few, inconsistent, and European populations have not yet been studied. 3 , 9 There has only been one prospective study that was conducted, and results showed exposure to particulate matter (PM) <10 µm in size (PM 10 ) and nitrogen dioxide (NO 2 ) were positively associated with incident cataract in the Korean National Insurance Service-National Sample Cohort (NHIS-NSC). In contrast to other studies of the health risks of air pollution, the authors reported there appeared to be a threshold effect in the risk profile.…”

Fine Particulate Matter and Age-Related Eye Disease: The Canadian Longitudinal Study on Aging

“…Relationships have been identified between PM 2.5 and visual impairment, 10 glaucoma, 11 , 12 and AMD, 13 but the results for cataract are unclear. 14 , 15 To our knowledge, all of the existing studies have been done in east Asia or the United Kingdom with none being done in the United States or Canada. Some evidence indicates that these findings are biologically plausible.…”

Impact on Eye Health Regarding Gaseous and Particulate Pollutants

“…Ultraviolet light exposure is one of the main sources in oxidative stress. The possible mechanism of the protective effect could be that increasing levels of tropospheric O 3 may shield the lens from ultraviolet light exposure (Choi et al, 2018). However, there is another possible reason for cataract formation in people who have household fuel air pollutants exposure, which is high temperature of the working environment.…”