Lung cancer smaller particular matter risk?

 Introduction 

Great health concern has been placed on the severe air pollution in China. Particular matters as the dominant air pollutants in Chinese cities (e.g. PM1, PM2.5 and PM10), have already been recognized as the Group I carcinogenic factor to lung cancer diseases in the world [1]. 

As reported by the State of Global Air 2020, particular matter air pollution has led to the mortality of around 500,000 infants across the world [2].

 Despite considerable efforts on the estimates of particular matter effects, especially for PM2.5 and PM10 [3–5], however, whether finer particular matter has the greater effect on human health has not been well understood in China and across the world.Several potential mechanisms have been proposed

 to explain the varying effects of size-fractioned particular matters. 

Biologically, particular matters including PM1, PM2.5 and PM10, can exert adverse effects on the physical health of human beings by the way of aggregating genetic damage [1]. 

With regards to the difference in health effects, firstly, there

 is high ratio of surface area to volume in finer than in coarser particular matters.

 This enables finer particular matter to more easily approach the deeper places in lung, such as lung alveoli [6, 7]. 

Secondly, the proportion of toxic chemical composition is usually higher in finer than in coarser particular matters. Such physicochemical property makes finer particular matter more easily cause detrimental effects on lung function and epigenetic alteration [8, 9].

Empirically, few attempts have examined the effects of PMs with different particle sizes.

 In general, the argument that smaller particular matters have greater effects on human health, is still debated. 

Many studies tend to support this argument, especially for research investigating the effects of PM1, PM2.5 and PM10 [10–12].

 Particularly, a time-series study performed in 65 Chinese cities between 2014 and 2017 indicated that the association with cardiovascular disease was stronger for PM1 than for PM2.5 and PM10 [7].

Similarly, as reported in the 33 Communities Chinese Health Study, the odds ratio of cardiovascular disease associated with a 10 μg/m3 increase in PMs was 1.12 (95% CI:1.05, 1.20) for PM1, which was higher than 1.06 (95% CI:1.01, 1.11) of PM2.5 [13]. 

By contrast, some studies report the greater effects of particular matters with larger particle sizes [14, 15] 

or the insignificant effects of some size-fractioned particular matters [16, 17]. 

For example, a case–crossover study performed in Barcelona of Spain suggested that the effect on cardiovascular mortality during Non-Saharan dust days was smaller for PM1 than for PM2.5 and PM10 [18].

Apart from inconsistent findings above, more efforts are required 

due to the three reasons.

Firstly, of research investigating the varying effects of particular matters with different particle sizes, most are single- or several-site studies [12, 19–21], 

while nationwide studies are quite limited [7, 22]. 

Hence, findings from previous studies are still not sufficient to

 conclude the greater effects of finer particular matters than those of coarser particular matters.

 Secondly, few studies pay attention to PM1 which is the dominant component of severe PM2.5 air pollution in Chinese cities [23]

. This is partly resulted from the unavailable data on PM1, especially at the national scale [7, 10]. 

Thirdly, it remains unknown whether smaller particular matter has the larger effect on lung cancer which has become the second-order of cancer incidences for the female in China [24], although numerous studies have suggested the effects of PMs (especially for PM2.5 and PM10) 

on lung cancer diseases [3, 25–27].

To fill the aforementioned gaps, this work used 

data collected from 436 Chinse counties between 2014 and 2016 to examine whether finer particular matter has the greater effect on the incidence rate of female lung cancer in China where particular matter air pollution is much more severe than developed countries.

 To answer the research question, three regression models were developed with different controls of time, location and socioeconomic covariates. 

We further investigated whether the findings are sensitive to the controls of smoking and drinking behaviors as well as additional air pollutant. Moreover, we tried to answer whether urban-rural division modifies the association of the incidence rate of female lung cancer with each of three particular matters (i.e. PM1, PM2.5 and PM10).

Ref

BMC Public Health. 2022 Feb 18;22:344. doi: 10.1186/s12889-022-12622-1

Smaller particular matter, larger risk of female lung cancer incidence? Evidence from 436 Chinese counties

Huagui Guo 1, Xin Li 2, Jing Wei 3, Weifeng Li 4,5, Jiansheng Wu 6,7, Yanji Zhang 8,✉