Heavy metal concentration in classroom dust samples and its relationship with childhood asthma: a study from Islamic Republic of Iran.

BACKGROUND: Classrooms are an important environment for young children as this is where they spend a large part of their time. AIMS: This study was designed to quantify the levels of heavy metals in classroom dusts in Shiraz, a city southwestern Iran. The potential association between heavy metal levels and childhood asthma was also investigated. METHODS: We selected 32 schools for collecting classroom dust samples during September-November 2016. The concentration of 10 heavy metals was measured in these dust samples by optical emission spectrometry. The diagnosis of childhood asthma was made using both the medical chart of each student and examination by an allergist. The data were analysed using SPSS, version 21.0. RESULTS: The concentration of heavy metals in classroom dust samples ranged from 7559 to 53 723.0 mg/kg (mean: 16 945.5 mg/kg) for Fe, 169.0 to 952.0 mg/kg (mean 288.9 mg/kg) for Mn, and 9.0 to 971.0 mg/kg (mean 258.8 mg/kg) for Pb. We found no correlation between heavy metals in classroom dust and childhood asthma. CONCLUSION: In comparison with studies reported elsewhere, the maximum levels of lead in our study were greater. A potential explanation for the lack of correlation with childhood asthma is the large mass of the particles, preventing them from reaching the lower airways. Nevertheless, special attention should be paid to reducing high levels of heavy metals in classroom dust in this area.

The Safety of Schools Based on Heavy Metal Concentrations in Classrooms' Dust: A Systematic Review and Meta-Analysis.

BACKGROUND: Classroom is where children spend much of their time in; this study aimed to identify the concentration of heavy metals in the classroom dust based on the results of various studies in the world using the published data up to years 2018. METHODS: Fifteen studies were selected for the study according to the inclusion and exclusion criteria. The mean concentration of 11 heavy metals including arsenic, barium, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel, and zinc was extracted. RESULTS: The highest mean concentration of heavy metal (mg/kg) in classroom dust was related to iron (3904.7, 95%CI: 3657.1-8154.3), zinc (429.9, 95%CI: 182.8-677.1) and barium (419.2, 95%CI: 274.7-253.7), respectively. Subgroup analysis showed the maximum concentration (mg/kg) of iron in Iran (16945.5), zinc in Hong Kong (2293.5), barium in China (979.8), manganese in Iran (288.9), lead in Iran (258.8), chromium in Ghana (381.3), copper in Hong Kong (274.4), nickel in Iran (50.1), cobalt in China(43.4), arsenic in China(13.7) and cadmium in Hong Kong(8.7). CONCLUSION: Even safe and healthy classrooms can threaten children's health by heavy metals. These metals are important since they are naturally found throughout the earth's crust, accumulate in the food chain and contaminate drinking water as well as alloys in school equipment.