Table 3. Risk of appendicitis associated with increases in the interquartile ranges of particulate matter ≤10 μm in diameter (PM₁₀) in various referent time intervals: a case-crossover analysis

Categories	Time intervals
	Admission day*	3-day moving average†	7-day moving average‡	14-day moving average§
Total	1.027 (0.994–1.060)	1.045 (1.007–1.084)	1.053 (1.005–1.103)	0.938 (0.871–1.009)
Sex
Male	1.045 (1.001–1.091)	1.076 (1.023–1.132)	1.103 (1.035–1.176)	0.994 (0.897–1.101)
Female	1.003 (0.954–1.054)	1.009 (0.954–1.066)	1.001 (0.935–1.071)	0.883 (0.795–0.981)
Age, yr
<10	1.129 (1.016–1.255)	1.140 (1.033–1.258)	1.235 (1.087–1.402)	1.042 (0.846–1.282)
10−19	1.013 (0.943–1.089)	1.032 (0.951–1.121)	1.021 (0.919–1.135)	0.897 (0.762–1.056)
20−29	1.013 (0.936–1.096)	1.003 (0.921–1.093)	0.991 (0.891–1.101)	0.839 (0.709–0.993)
30−39	0.998 (0.929–1.072)	1.013 (0.926–1.109)	1.024 (0.914–1.148)	0.900 (0.753–1.075)
40−49	0.985 (0.891–1.088)	1.054 (0.937–1.184)	1.073 (0.936–1.231)	0.940 (0.766–1.153)
50−60	1.063 (0.964–1.171)	1.056 (0.939–1.188)	0.993 (0.859–1.149)	1.053 (0.841–1.319)
≥60	1.069 (0.946–1.207)	1.046 (0.914–1.198)	1.122 (0.955–1.318)	1.111 (0.851–1.149)
Season
Warm seasonΠ	0.865 (0.817–0.916)	0.807 (0.756–0.860)	0.690 (0.637–0.746)	0.420 (0.369–0.478)
Cold season¶	1.252 (1.192–1.316)	1.424 (1.343–1.509)	1.716 (1.593–1.849)	2.632 (2.334–2.967)

All models were adjusted for daily mean temperature and humidity.
Current day: PM₁₀ exposure level on the day of hospital admission.
PM₁₀ exposure level between current hospital admission day and two days before hospital admission (lag 0‒2).
PM₁₀ exposure level between current hospital admission day and 6 days before hospital admission (lag 0‒6).
PM₁₀ exposure level between current hospital admission day and 13 days before hospital admission (lag 0‒13).
The warm season runs from April to September.
The cold season runs from October to March.