Industrial or natural incense: different emissions!

These sticks are used at local producers, in Hindu or Buddhist temples, to perfume the atmosphere as they are consumed.  But although they offer a pleasant smell, incense sticks also release many pollutants through the atmosphere including particles, carbon monoxide and dioxide, nitrogen oxides, benzene, formaldehyde, etc.  While they consume they are used outdoors at the other side of the world, in our homes they are mainly used indoors!

Everything began in 2006 when a large incense sticks distributor who had been severely criticised in an article published in the "Que Choisir" magazine, decided to ask CSTB to carry out emission tests.  A series of tests were carried out in a room in the MARIA experimental house on the CSTB Champs-sur-Marne site;   43 products (sticks, cones, candles, perfume concentrates) were analysed using an analysis protocol specially developed for the occasion.  Its purpose was to measure emissions of the main released pollutants (particularly benzene and formaldehyde) during and after combustion.  These measurements made at full scale in the MARIA house evaluated the potential exposure level of users of these products to VOCs and formaldehyde, so that health risks incurred by users can be estimated as a function of usage frequencies.

Candles pollute less than incense

Stick 1 (yellow): industrial incense - Stick 2 (green): natural incense

Benzene and formaldehyde emissions from sticks and incense cones are highest during combustion and for the first hour after combustion, and then reduce significantly in the study room due to air replacement through the ventilation system (0.6 vol/h).  It can be seen that incense cones release more formaldehyde than incense sticks.  Furthermore, the concentration of pollutants increases as the mass of burnt product increases.  Benzene and formaldehyde emissions from candles are much lower than from incense.  On the other hand, a slight increase in formaldehyde concentrations was observed for candles after combustion, probably as a result of chemical reactivity occurring indoors.

It is thus found that the use of some consumption products such as air fresheners add isolated pollution to the general level of indoor air pollution that integrates the contribution of outdoor air, "continuous" emission sources (construction and decoration products, furniture, etc.) and "discontinuous" emission sources (maintenance products, indoor deodorants, human activities, etc.).  Therefore, the objective is firstly to limit emissions from all emission sources in indoor environments, and secondly to make sure that air renewal and ventilation requirements in indoor environments are fulfilled.  Furthermore, manufacturers should provide appropriate recommendations for the use of "isolated" sources (particularly maintenance products and indoor deodorants).

Manufacturers adapt

The methodology presented was used for the evaluation and quantification of severe and chronic health risks incurred by the population exposed to emissions of benzene and formaldehyde by incense and indoor candles, after the production of exposure scenarios.  After seeing the results, manufacturers made significant changes to their products (reducing the burnt mass) and abandoned some formulations to replace them with other less emissive formulations.   Exposure scenarios were used to recommend a frequency of use of these indoor perfumes as a function of the health and carcinogenic risks incurred in the long term.

43 products (sticks, cones, candles, perfume concentrates) were analysed using a specially developed analysis protocol. Its purpose was to measure releases of the main released pollutants.

Along the Incense Road: from New Delhi to… Champs-sur-Marne!

France 2 Journalists who had read an article on the subject published in the Environnement, Risques & Santé magazine by François Maupetit (CSTB) and Fabien Squinazi (City of Paris Health Laboratory) in 2009, wanted to know more about the impact of these products on indoor air quality and to shoot a few sequences on measurements of polluting emissions made at CSTB in the MARIA house.  They brought in a stick of Indian industrial coated incense bought in Paris and asked CSTB to test it and compare its emissions with emissions from a natural sandalwood-based incense.
The results speak for themselves;  for a burnt mass equivalent to the mass of the natural stick, benzene emissions produced by the industrial stick were four times higher and formaldehyde emissions were almost twice as high.  Professor Squinazi has no doubt "When used repeatedly for a long period in confined atmospheres, these incense products are carcinogenic.  They should be withdrawn from the market or their formulation should be changed."