Measurement

In workplace atmospheres

To measure dust exposure levels at the workplace, the following European standards provide the necessary technical guidance to implement a dust monitoring strategy:

EN 689: Workplace atmospheres-Guidance for the assessment of exposure by inhalation to chemical agents for comparison with limit values and measurement strategy, 1995, CEN.

EN 1232: Workplace atmospheres-Pumps for personal sampling of chemical agents-Requirements and test methods, 1997.

To determine the quartz/cristobalite content in the collected dust, two different analytical techniques can be used: Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).
Here are the reference standards for both techniques:
AFNOR- XP X 43-243 : Dosage par spectrométrie infra rouge à transformée de Fourier de la silice cristalline - Echantillonnage par dispositif à coupelle tournante ou sur membrane filtrante.
AFNOR XP X 43-295 : Détermination par rayons X de la concentration de dépôt alvéolaire de silice cristalline- Echantillonnage par dispositif à coupelle rotative.
MDHS 101:  Crystalline silica in respirable airborne dusts- Direct-on-filter analyses by infrared spectroscopy and X Ray diffraction.
NIOSH 7602: Silica, crystalline by IR.
NIOSH 7500: Silica, crystalline by XRD.

Industry dust monitoring protocols:

A dust monitoring protocol is provided in Annex 2 of the Social Dialogue Agreement on Workers’ Health Protection through the Good Handling and Use of Crystalline Silica and Products Containing it, see www.nepsi.eu. It summarises the general requirements from the European Standards EN 689 and EN 1232 mentioned above.

IMA-Europe has developed its own Dust Monitoring Protocol with a view to collect representative and comparable dust exposure data at the level of the industrial minerals sector across Europe. The statistical reliability of the data collected means that it will also be valuable for future epidemiological studies.
The dust monitoring programme was launched in 2000, more than 20 industrial mineral companies have been collecting exposure data following the common protocol since then.

Since 2006, the project is managed by the Institute for Risk Assessment Studies (IRAS), University Utrecht, & Netherlands Expertise Centre for Occupational Respiratory Disorders (NECORD).
Considering data collected up to winter 2008/2009, 17 sampling campaigns took place in 24 companies at 93 different worksites and consisted of 12,647 measurements of respirable dust and 10,075 measurements of respirable quartz.

Results:

Two different measures that describe the probability of exceeding these OELs were reviewed: probability of exceedance and probability of overexposure. Both measures indicated that the probability of exceeding especially the lower OELs for both dust and quartz was relatively high for workers in this sector in several occasions. However, overall downward trends in exposure levels for respirable dust and respirable quartz ranging (from -2 to -26%) per sampling campaign for the majority of job titles were observed in the IMA database over the years 2000-2009.

Prof. H. Kromhout and R. Houba who analyse it consider that the potential of this unique industry-wide exposure database is very high. Considerable improvements in data quality have been achieved during the project, but improvements are still possible, especially with regard to repeated measurements for individual workers within campaigns. The IMA Dust Monitoring Programme Database contains personal measurements of more than 2,000 monitored workers who are assumed to be representative of in total 5,000 workers from industrial minerals production. This unique prospective exposure database will prove to be very valuable in evaluating time trends in exposure to respirable dust and its crystalline silica content and when monitoring the health effects due to exposure to respirable mineral dust among these workers.

Participation from more industrial minerals producers in this IMA-Europe project is always welcome, please contact us for more information.

 

Measurements in bulk materials

A method has been developed in the industrial minerals industry for the purpose of determining the “size weighted relevant fine fraction” within the bulk material. It has been used in the industry and by institutes previously under the acronym SWeRF. The method only measures the fraction of the substance (e.g. fine dust or fine crystalline silica) present in the material. A procedure has been launched to standardise the method through CEN (the European Committee for Standardisation). The method does not by itself estimate levels of occupational exposure to hazardous substances and it is not a substitute for workplace measurements.

This method describes two procedures which can be used to estimate the size weighted fine fraction (FF) in bulk materials. The method can be used for comparing the fine fraction in different bulk samples. This standard uses the term fine fraction to indicate that it does not analyse airborne particles, but it evaluates the proportion of particles in a bulk material that, based on their particle size, have a potential to be respirable if they were to become airborne.

It also allows for the size weighted fine fraction of crystalline silica (FFcs) particles in bulk materials to be evaluated in terms of weight percent if the fraction separated is subsequently analysed by a suitable method.

The evaluation of bulk materials using FF is complementary to determining the dustiness according to EN 15051-1. The difference between the two standards is that FF quantifies the fine fraction in a bulk material while dustiness quantifies the respirable, thoracic and inhalable dust made airborne from the bulk material after a specific activity (it characterizes the material with relation to the workplace atmosphere when working with the bulk material).

The FF provides useful information to users and allows them to compare bulk materials for the content of fine fraction particles.

The methodCharacterization of bulk materials — Determination of a size-weighted fine fraction and crystalline silica content” consists of the following parts:

Part 1: General information and choice of test methods;

Part 2: Sedimentation method;

Part 3: Calculation method.

Part 1 describes the requirements and choice of test method. It provides the user with guidance on how to select the method as well as the preparation of the sample and determination of crystalline silica by XRD and FT-IR. The method in Part 2 uses a liquid sedimentation technique to separate the fine fraction, which is then analysed for its substance of interest, e.g. crystalline silica. Part 3 describes an alternative method, which calculates the fine fraction from a measured particle size distribution and assumes that the measured crystalline silica content in the bulk and fine fraction are the same.

Link to SWeRF calculation xls sheet (2015)

List of labs able to do the SWeRF measurements. (also in pdf)