Background, Aim and Scope:
All across Europe, people live and work in indoor environments. On average, people spend between 85 to 90% of their time indoors (homes, workplaces, cars, and public transport means, etc.) and are exposed to a complex mixture of pollutants at concentration levels, which are often up to five times higher than outdoors. These pollutants are emitted by different sources indoors and outdoors and include Volatile Organic Compounds (VOCs), carbonyls (aldehydes and ketones) as well as other chemical substances often adsorbed on particles. Moreover, legal obligations opposed by legislations such as the European Union’s General Product Safety Directive (GPSD) and Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH), increasingly require detailed understanding of where and how chemical substances are used throughout their life-cycle to be able to control emissions from sources aiming at reduction of adverse health effects. Scientific-sound human risk assessment procedures based on qualitative and quantitative human exposure data allows better characterization of population exposures to chemical substances. In this light, the current paper compares inhalation exposures to three EU priority substances, i.e., formaldehyde, benzene, and acetaldehyde.
Materials and Methods:
48h average inhalation exposures were modeled on the basis of concentrations in three microenvironments comprising indoor, outdoor, and in-transit microenvironments, and respective population time-activity data generated by three European Commission funded urban population exposure studies in and outside Europe, i.e., HEXPOC, INDEX, and AIRMEX. The 48h modeled exposures were compared to measured 48h average personal exposures. The partial micro-environmental contribution to the total daily inhalation exposure of formaldehyde, benzene, and acetaldehyde was estimated. Both modeled and measured inhalation exposures were compared to historical concentration data and to the EU annual ambient benzene air quality guideline (5 ?g/m3 – to be met by 2010) and recommended (the INDEX project) 30-min average formaldehyde limit value (30 milligram/m3).
Results:
The formaldehyde and acetaldehyde concentrations in the indoor microenvironment were higher than in the outdoor or in-transit microenvironments. Together with the fact that a dominating fraction of time is spent indoors (87%), the total inhalation exposure is mostly driven by the time spent indoors. The benzene concentrations were typically higher when moving (in-transit) than in the indoor or outdoor microenvironments. Still, the total daily inhalation exposure was determined by indoor microenvironments at lower benzene concentrations, because the majority of the time was spent in this microenvironment.
Discussion:
The approach used in the current paper faced three challenges dealing with diversity, scarcity or missing in-transit, and population time-activity data forcing careful interpretation of the results. Compared to previous decades, both modeled and measured inhalation exposures suggest that the indoor air quality improved. However, still it is likely that the annual ambient benzene air quality guideline of 5 milligram/m3 in the EU and recommended formaldehyde 30-min average limit value of 30 ?g/m3 are exceeded by a substantial part of the population living in urban areas. Considering multimedia and multi-pathway exposure to acetaldehyde, the biggest exposure contribution was found to be related to dietary behavior rather than to inhalation.
Conclusions:
In the present study, inhalation exposures of urban populations were assessed on the basis of monitoring and modeling methods using data produced by three exposure studies HEXPOC, INDEX, and AIRMEX. Both modeled and measured inhalation exposure concentrations suggest that the current indoor air quality improved compared to previous decades, however, also suggests that still a significant part of the populations living in cities inside and outside Europe exceed the annual ambient benzene air quality guideline of 5 ?g/m3 in the EU and recommended (INDEX-project) formaldehyde 30-min average limit value of 30 ?g/m3. This part of the population may include subpopulations such as children, pregnant women, and the elderly known to be more vulnerable in terms of health effects. To reduce exposures and consequent health effects, adequate measures must be taken to diminish emissions from materials and products that especially emit formaldehyde and benzene in indoor air. Besides emission reduction, mechanisms to effectively monitor and manage the indoor air quality should be established. This mechanism could be developed by the setting up of appropriate EU indoor air guidelines.
Recommendations and
Perspectives:
To reduce exposures and consequent health effects, adequate measures are recommended to be taken aiming at lowering indoor emissions from materials and products especially emitting formaldehyde and benzene. The development of appropriate EU indoor air quality guidelines, providing mechanisms to effectively monitor and manage the indoor air quality, should be established.
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