Ambient air pollution and meteorological factors associated with hand, foot, and mouth disease risk in Shenzhen, China: a time-series study

Abstract

In China, hand, foot, and mouth disease (HFMD) persists as a prevalent infectious disease with high transmissibility. Nevertheless, the link between environmental determinants and HFMD incidence has not been fully elucidated. The study assessed associations between air pollution, meteorological conditions, and HFMD incidence in Shenzhen, China, while also evaluating shifts in these associations before and after the Enterovirus 71 vaccine and during the COVID-19 epidemic. Daily data on HFMD cases, air pollutants (such as PM 2.5 , PM 10 , SO 2 , NO 2 , CO, and O 3 ), and meteorological variables (including mean temperature, relative humidity, atmospheric pressure, and wind speed) were collected for the period from 2013 to 2022. Associations were assessed using distributed lag non-linear models (DLNM), accounting for immediate and delayed effects. Spearman correlation analysis showed that HFMD was positively correlated with SO₂, mean temperature, relative humidity, and wind speed, and negatively with PM₂.₅, PM₁₀, NO₂, CO, and atmospheric pressure. DLNM models revealed that SO₂ and CO both elevated cumulative risk at extremely high concentrations, with SO₂ showing delayed effects. However, SO₂ unexpectedly displayed protective effects in single-lag analysis. NO₂ exhibited a U-shaped risk at extreme concentrations despite an overall decreasing trend. O₃ showed dual peaks, with protective effects at extremely high concentrations after lag 1. PM 2.5 and PM 10 showed risk peaks at low concentrations but protective effects at extremely high concentrations. Temperature exhibited a dual-peak risk pattern at extremely low and extremely high temperatures, with extreme heat producing sustained effects and extreme cold shorter-lived risk. HFMD risk increased under conditions of extremely high humidity. In general, the risk associated with atmospheric pressure rose as pressure levels increased, and asymmetric lagged effects were observed at both low- and high-concentration extremes. Extremely high wind speed causing short-term harm and extremely low wind speed leading to delayed cumulative risk. Meteorological factors exhibit more consistent associations than air pollutants. Mean temperature showed a dual-peak distribution with persistent effects from high temperatures, while atmospheric pressure presented long-lasting impacts of low pressure. There is a positive correlation between relative humidity and the incidence of HFMD. Air pollutants showed inconsistent associations with HFMD. These findings support targeted public health interventions for meteorological factors.