Background Urban forest environment is an important part of urban environment. Short-term exposure to forest environment is beneficial to human physical and psychological health. However, currently there is no research focusing on the changes of health effects of general population after exposure to forest environment for a few hours. In addition, it's still unclear whether different air pollutant levels between urban and suburban forest parks will affect human health.

Objective This study aims to explore the effects of short-term exposure to different forest environments on human cardiopulmonary and psycho-emotional indicators.

Methods From August to October in 2018, two forest parks, one in urban and the other in suburban areas, were selected as study sites, and a total of 1 498 visitors who stayed in the park area for 0.5-8 h were recruited as study subjects. Blood pressure, lung function, and psycho-emotional indicators were measured before and after forest environment exposure. Air pollutant data from two monitoring stations closest to the study sites were collected to estimate the air quality levels. Mann-Whitney U test was used to compare the concentration of pollutants in the two parks, paired t test was used to compare the health indicators before and after forest exposure, and t-test and multiple linear regression were used to analyze the relationships between the changes of health indicators and different forest environments.

Results The concentrations of most air pollutants in suburban forest environment were lower than those in urban forest environment (except O₃). Compared with the time point before entering forest environment, both systolic blood pressure (SBP) and diastolic blood pressure (DBP) of the study subjects decreased significantly (t_SBP=19.035, t_DBP=6.283, P < 0.001), and SBPdecreased from (132.96±20.27) mmHg to (125.77±17.82) mmHg showed a steeper decrease than DBPdecreased from (78.57±10.79) mmHg to (77.21±10.99) mmHg. When comparing between two forest environments, the visitors exposed to urban forest environment showed more decline in DBP than those exposed to suburban forest environment (Δ_urban=-2.85 mmHg, Δ_suburban=-1.13 mmHg, t=3.547, P < 0.001), but the visitors exposed to suburban forest environment showed better improved respiratory system as the forced expiratory volume in the first second (FEV₁) was elevated (t=7.151, P < 0.001), and there was no difference of the visitors in urban forest (t=0.529, P=0.598). The multivariate analysis results showed that regional factor was not decisive in producing this difference. Further analysis of the visitors exposed to suburban forest environment showed that their FEV₁ and forced expiratory volume in the sixth second (FEV₆) increased by 0.09 L and 0.05 L on average, respectively, and lung ventilation function indicators FEV₁/FEV₆ (increased from 0.80±0.15 to 0.82±0.14, t=4.290, P < 0.001) and forced expiratory flow at 25%-75%FEF_25%-75%, increased from (2.36±1.08) L·s^-1 to (2.46±1.07) L·s^-1, t=4.296, P < 0.001 were both improved. In terms of psycho-emotional indicators, the scores of subscales of tension, anger, depression, and panic and the total score of total mood disturbance (TMD) decreased, showing that the negative emotions of the subjects were significantly reduced.

Conclusion A short-term forest environment exposure can significantly improve the cardiovascular, respiratory, and psychological health of people, including lowering blood pressure, increasing lung capacity, and lifting mood.