Elemental analysis of dust trapped in air conditioner filters for the assessment of Lahore city’s air quality

Heavy metals in indoor dust: Spatial distribution, influencing factors, and potential health risks

Given the large proportion of time that people spend indoors, the potential health risks posed by heavy metals in the indoor environment deserve greater attention. A global-scale assessment of heavy metal contamination in indoor dust was conducted in this study based on >127 articles published between 1985 and 2019. The pollution levels, spatio-temporal variations, sources, bioaccessibilities, influencing factors, and health risks of heavy metals associated with indoor dust were analyzed. Children's blood lead levels (BLLs) were also estimated using the integrated exposure uptake biokinetic model. The results indicated that the median concentrations of Cu and Zn in 71.9% and 71.0% of the study sites surpassed the corresponding permissible limits, 100 and 300 mg/kg, respectively; thus, their control should be given priority. Heavy metal concentrations in indoor dust from different areas of the world varied greatly, which was closely associated with the type of local human activities, such as mining, melting, e-waste recycling and Pb-related industries. The bioaccessibilities of some key elements, e.g., Pb, Cd, Cu, and Zn, in household dust were high. The levels of heavy metals in indoor dust were mainly affected by a combination of outdoor and indoor sources and related critical factors, and future studies should focus on quantifying the contributions of different sources. Based on the health risk assessment, dust Pb exposure is a major health concern in e-waste recycling areas, which warrants greater attention. 49.8%, 36.8% and 14.4% of study sites showed BLLs exceeding 35 μg/L (threshold limit in Germany), 50 μg/L (threshold limit in the USA), or 100 μg/L (threshold limit in China), respectively. Finally, Pb exposure from indoor dust represents a major contributor to children's blood Pb poisoning in many developing countries. This study details the overall heavy metal contamination status of indoor dust and provides insights for policymakers with respect to pollution prevention measures.

Elemental compositions of particulate matter retained on air condition unit's filters at Greater Doha, Qatar

Elemental composition of airborne dust samples retained by internal filters of air condition units (ACUs) was determined at 12 locations of Doha city, state of Qatar. Twenty-four elements: Al, Ca, Mg, Fe, Na, K, Ti, Zn, P, Sr, Mn, Ba, Cu, Cr, Ni, Pb, V, Mo, Li, Co, Sb, As, Cd, Be, were analysed by ICP-OES technique after acid digestion of the samples. The analysed components reflect 20.6% of the total sample mass. Similar or lower concentration values have been found for As, Cd, Cr, Cu, Mn, Ni, Pb, V, Zn, Al, and Fe compared to the international context of upper crust concentrations, NIST SRM (urban dust), published local dust information of outdoor, and surface terrestrial deposit (STD) counted for 7.2, 0.7, 91.8, 192.8, 369.7, 68.6, 65.3, 52.1, 824.3, 19,791, 20,508 mg/kg, respectively. The coefficient of correlation (p ≤ 0.05) showed significant association of ACUs dust elemental compositions with the main components of the local earth crust and surface deposits, ranging from the lowest 0.77 (Mg-Fe) to the highest 0.98 (Al-Fe), while Ni and V, typical anthropogenic pollutants, are also strongly correlated (0.86). These strong correlation relationships can be interpreted as the contribution of outdoor particulate to the indoor dust. Dendrogram of metal/Al ratios, based on Euclidean distance calculation and average linkage clustering method, distinguished three typical groups. Studying the enrichment factors of the three groups indicated elevated levels of Zn (131), Pb (49), Cu (32), Cd (8) and Ni (5) found indoors compared to the background composition of STD especially at locations in the industrial zone. The major elemental composition of the samples reflects the typical mineral composition of the local dust, while the trace composition demonstrates the influence of indoor sources. The collected ACU filter dust samples show significant contribution of outdoor mineral particles, non-exhaust traffic emission, industrial sources, as well as the influence of indoor activity such as smoking.

In vitro inhalation/ingestion bioaccessibility, health risks, and source appointment of airborne particle-bound elements trapped in room air conditioner filters

The airborne particle-bound elements (Ca, Fe, Al, Mg, K, Na, Zn, Mn, P, Pb, Cu, Sr, Ti, Ba, Cr, Ni, As, Sb, Cd, Co, and V) trapped in room air conditioners' filters (filter dusts) during recirculating indoor air from different types of rooms were analyzed, and the objectives of this study were to assess the potential sources of those elements and their potential health risks via inhalation/ingestion exposure. Main crustal elements such as Ca, Fe, Al, Mg, and K with an average value of 60.6, 17.9, 11.3, 7.58, and 6.90 mg g^-1, respectively, are the preponderant elements, and the mean values of main toxic elements were 2230, 344, 508, 85.7, 71.5, 36.0, 8.02, and 16.9 mg kg^-1 for Zn, Cu, Pb, Cr, Ni, As, Cd, and Sb, respectively. The enrichment factors indicated the significant enrichment of Cd, Pb, Cr, Cu, Sb, and Zn in the filter dusts. Four potential sources with the contributions of 33.5, 29.1, 22.6, and 14.8%, respectively, were identified by absolute principal component scores-multiple linear regression analysis (APCS-MLR). Enrichment factor and APCS-MLR model reveal the outdoor input of toxic elements. In vitro inhalation and ingestion bioaccessibility of toxic elements showed elemental and in vitro procedure dependence. There are potential carcinogenic risks via ingestion exposure and no non-carcinogenic risks to both children and adults based on bioaccessible contents of toxic elements. This study reveals the potential health risks posed by the particle-bound elements.

Quantitative filter forensics for indoor particle sampling

Filter forensics is a promising indoor air investigation technique involving the analysis of dust which has collected on filters in central forced-air heating, ventilation, and air conditioning (HVAC) or portable systems to determine the presence of indoor particle-bound contaminants. In this study, we summarize past filter forensics research to explore what it reveals about the sampling technique and the indoor environment. There are 60 investigations in the literature that have used this sampling technique for a variety of biotic and abiotic contaminants. Many studies identified differences between contaminant concentrations in different buildings using this technique. Based on this literature review, we identified a lack of quantification as a gap in the past literature. Accordingly, we propose an approach to quantitatively link contaminants extracted from HVAC filter dust to time-averaged integrated air concentrations. This quantitative filter forensics approach has great potential to measure indoor air concentrations of a wide variety of particle-bound contaminants. Future studies directly comparing quantitative filter forensics to alternative sampling techniques are required to fully assess this approach, but analysis of past research suggests the enormous possibility of this approach.

Instrumental neutron activation analysis for the study of size-fractionated airborne particulate matter samples

In order to devise methodology to study various environmental matrices 28 pairs of coarse and fine air particulate samples were collected in the vicinity of an automotive workshop located at Tasmasipabad on Chaklala Road, Rawalpindi. The samples were collected using a Gent sampler and polycarbonate filters during the period 7 to 27 April 2009. These samples were analyzed using instrumental neutron activation analysis (INAA) using the low power Pakistan Atomic Research Reactor-2 (PARR-2). Reference materials (RMs) IAEA-SL1 and IAEA-S7 were used for calibration and quality assurance (QA) purpose. The gravimetric data for these samples were found to exceed the PM2.5 and PM10 national limits. Up to 34 elements were measured using the INAA optimized procedure.