FEATURE ARTICLE

Closing on the gap on spray inhalation safety assessments

Published: October 30, 2017

British Aerosol Manufacturer’s Association (BAMA) Technical Director, Paul Jackson, introduces the key principles of inhalation safety assessment.

The Aerosol Dispensers Directive (ADD), originally drawn up in 1975, is one of the oldest pieces of EU legislation. It was originally designed to allow marketers to sell their aerosols in all Member States of the Common Market by ensuring safe movement and circulation, and guaranteeing safety for consumers and other users. Over the years it has been amended four times to reflect changing levels of concern in relation to hazards such as flammability and exposure via inhalation.

A particular hazard for aerosols is the possibility of inhaling the spray particles, this concern was specifically addressed by the Aerosol Dispensers Directive in 2008 when an obligation was placed on the marketer to analyse the hazards in order to identify those which apply to his aerosol dispensers. This obligation includes consideration of inhalation and droplet size of the spray, although no details are specified. So how can safety assessors determine the inhalation risks of aerosols?

In many ways the ADD obligation reflects REACH’s requirement for suppliers to carry out a Chemical Safety Assessment (CSA) of any chemicals they place on the market. So in time, the ADD hazard analysis may be simply a matter of checking that the use complies with the ES (exposure scenarios) listed in the safety data sheets for the ingredients. However, REACH will not be fully implemented for several years and so in the meantime, BAMA, working with colleagues across Europe, has developed a five stage approach for the ‘hazard analysis’ which is based on the CSA.

The five stages are:

  1. Collect toxicological data on the ingredients
  2. Hazard assessment
  3. Tiered exposure assessment
  4. Risk characterization
  5. Pre-market check.

Key to this approach is to identify if any ingredients in the formulation have toxicological hazards and only carry out assessment of these chemicals. Stage 5 should be a routine practice for the marketer. The approach is described in the Figure and in more detail below.


1. Collect toxicological data

The first step is to collect and review available toxicological data to identify those ingredients, if any, that give cause for concern. The primary source of information will be the safety data sheets for each ingredient, although at the present time their quality is variable. So, until REACH is fully implemented it is advised that other data should be referred to in addition, for example, work exposure limits and the BAMA Hazard Summary Profiles.

2. Hazard assessment

The second stage is to identify if any hazards identified are present in sufficient concentrations to be a potential hazard for human health. This is a three-step process: First, identify the hazards present in the formulation, then determine the level of exposure for humans that is hazardous, and finally check whether the ‘ingredients of concern’ are present in sufficient concentration to be a hazard to human health.

During this process it is important to consider the possibility for hazardous by-product intermediates being formed during processing or storage of the filled aerosols. Another possibility is where one ingredient is a strong acid, but another that is a strong base. The mixture could be either acidic or alkaline and be an irritant or be neutral and give rise to no toxicological hazard.

3. Tiered Exposure Assessment

Aerosols have a wide variety of applications and if the Hazard Assessment determines that the formulation has the potential to give rise to hazard to human health, then it is necessary to assess the exposure to using the aerosol for a range of conditions. An exposure assessment requires knowledge of expected conditions of normal use (i.e. used as directed) and reasonably foreseeable conditions of accidental misuse (e.g. misdirection of the spray). The exposure will be determined by the nature of the dispensed product, the particle size distribution of the spray, the concentration in the room where it is being used and the time of exposure.

This can be assessed by a tiered approach; firstly, consider how the product is delivered (e.g. spray, gel, foam – exposure by inhalation will be less relevant for foams and gels than for sprays). The second stage is to screen the ingredients by assuming a worst-case scenario in which exposure is to the entire contents in ‘one go’. For many aerosol ingredients the process will end here because there is ‘no cause for concern’ or because it is clear that reformulation is necessary. The third stage is to model or measure actual exposure during use, this can be quite complex for spray products and factors such as spray particle concentration and size need to be known.

4. Risk Characterization

Once the exposure to the spray has been estimated, modelled or measured, the next stage is to assess the risk. This is done by comparing the outcome of the exposure assessment with the relevant toxicological effects determined in Stage 2. Although the various EU product regulations use broadly similar methodologies, the way that they characterise risk varies. For example, under REACH the process is known as the Risk Characterization Ratio (RCR), whereas for cosmetic products it is the Margin of Safety (MoS). If at this stage there is ‘cause for concern’ about any ingredient then it is very likely that the aerosol will need to be reformulated.

5. Premarket Check

The final stage is to ensure that the risk management measures are in place (e.g. labelling).

This process is described in more detail in Module 1 of The BAMA Standard for Consumer Safety and Good Manufacturing Practice, which includes advice of where to get toxicological data and a discussion of the complexities of modelling and measuring inhalation exposure to spray products.

The BAMA Standard is available to Non-member from on the BAMA Website www.bama.co.uk.

The Advice is also available, in a slightly different format from the European Aerosol Federation (FEA), www.aerosol.org/publications-news/publications/guidance.

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