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Exposure related observations in humans: other data

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Endpoint:
exposure-related observations in humans: other data
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2004-2007
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Test procedure in accordance with national standard methods with acceptable restrictions. The data are considered to be of high quality and generated with conservative or realistic assumptions for the following reasons: work and evaluation was supervised by a single study director, sampling was performed based on clear written protocols and by a predefined and representative sample of manufacturing sites (protocol: MDHS 47/2)

Data source

Reference
Reference Type:
publication
Title:
A small survey of exposure to rubber process dust, rubber fume and N-nitrosamines
Author:
Keen C.
Year:
2010
Bibliographic source:
Health and Safety Executive publication, RR819 Research Report, Derbyshire, UK

Materials and methods

Type of study / information:
monitoring data from different exposure sites in the UK
Test guideline
Qualifier:
according to guideline
Guideline:
other: MDHS 47/2 (Determination of rubber fume (measured as cyclohexane soluble material) in air)
Deviations:
not specified
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
rubber fume in general
IUPAC Name:
rubber fume in general
Details on test material:
Rubber fume is defined as fume evolved in the mixing, milling and blending of natural rubber or synthetic elastomers, or of natural rubber and synthetic polymers combined with chemicals, and in the processes which convert the resultant blends into finished products or parts thereof, and including any inspection procedures where fume continues to be evolved.

Method

Details on study design:
methodology:
On all site visits were determined using methodology described in MDHS 47/2. Rubber fume was determined as the cyclohexane soluble fraction of the sample.
The air sampling strategy focussed on measurement of worker exposures. Hence the majority of samples taken were personal samples, with the sampling device mounted in the worker’s breathing zone. A small number of static (background) samples were taken but the results of these are not considered to be representative of worker exposures and have not been included in the statistical analysis of data. Samples were taken over a sufficiently long period as to be representative of full shift exposure, and hence the results have been used, in conjunction with information of shift length, to calculate 8 hour time weighted average exposures. Typically the sampling duration was at least 50% of the work shift. At each site, workers were sampled in all areas where there was exposure potential. At all sites visited, work on the day of the visit was generally considered as being normal. Attempts were made to capture typical, rather than worst case, exposures. At the smaller sites, a significant proportion of the overall workforce was sampled. At larger sites, it was necessary to select a sample of the potentially exposed workforce whose exposures were considered representative of the whole workforce.

site selection:
Published literature suggests that fume exposures in GRG sector are slightly higher than new and retread tyre making. For these reasons, the project focussed on the GRG sector. 9 sites between 2004 and 2007 were visited for the measurements, four of these were performed for reactive purposes.
Exposure assessment:
measured

Results and discussion

Results:
A total of 75 exposure measurements were made for rubber fume at 9 sites between 2004 and 2007. The limit of detection of the analytical method is dependant upon the volume of air sampled, and on the results of blank determinations. This varied slightly between visits, but was typically around 0.1 mg/m3. For the purpose of statistical analysis a numerical value of LOD/2, 0.05mg/m3, was used for these results. Seventeen (57%) of the results from the Disease Reduction Programm (DRP) visits were All sites visited for the 2007 DRP survey were judged to have some deficiencies in their exposure control strategy. These ranged from relatively minor to significant. Four of the 5 sites were performing compression or injection moulding with no LEV. In addition, 2 of the 4 sites visited for reactive purposes were running moulding presses without LEV. The LEV was inadequate at another of these sites due to a combination of poor design and inadequate maintenance. In total, of the 9 sites visited by HSE between 2004 and 2007 to assess rubber fume exposure, six were running moulding presses with no LEV, and the LEV was inadequate at one other site. Only 2 of these sites were deemed to have suitable, well maintained LEV installed to control rubber fume exposures.
Of the 5 sites visited for the 2007 DRP survey, only 1 had had a suitable and sufficient COSHH assessment, 2 sites had conducted recent (within the past 5 years) exposure monitoring. Detailed information on these aspects of the exposure control strategy was not available from the 4 reactive visits.
RPE (Respiratory Protective Equipment) was used as a rubber fume exposure control at one of the sites visited for the 2007 DRP survey. However, there were inadequacies within the RPE programme, for example workers with beards were observed wearing equipment which relied upon the face seal for protection.
Exposure control strategies generally paid little, if any, regard to the potential for dermal exposure to rubber fume. Cured, and uncured rubber was handled at several of the sites visited without gloves. There may be dermal risks associated with the handling of uncured, or freshly cured rubber, although these are not necessarily linked to dermal exposure to rubber fume. The absence of COSHH assessments at most of the sites visited make it difficult to evaluate whether dutyholders have adequately considered the potential for dermal exposure during rubber curing.

Any other information on results incl. tables

Rubber fume exposures (mg/m3) measured by the Health and Safety Laboratory (HSE) between 2004 and 2007:

   number of sites  number of measurements  exposure range  mean  geometric mean  median  results <LOD  results >WEL  sites >WEL
 reactive visits  4  45  ND - 1.75  0.27  0.16  0.16  12  6  2
 DRP survey  5  30  ND - 0.53  0.15  0.1  0.08  17  0  0
 all data  9  75  ND - 1.75  0.22  0.14  0.13  29  6  2

Applicant's summary and conclusion

Conclusions:
The Health and Safety Laboratory has made 75 rubber fume exposure measurements at 9 different GRG sites between 2004 and 2007. The geometric mean of these data is 0.14 mg/m3, the median is 0.13 mg/m3. The rubber fume WEL of 0.6 mg/m3 was exceeded at two sites. Six measured exposures, 8% of the measurements taken, exceeded the WEL. In conclusion of the measured data the WEL of 0.6 mg/m3 could therefore be taken as 90th percentile as a worst case.
Executive summary:

The Health and Safety Laboratory has made 75 rubber fume exposure measurements at 9 different GRG sites between 2004 and 2007. Exposures were mostly controlled to less than the UK Workplace Exposure Limit (WEL) of 0.6 mg/m3 8 hour time weighted average (TWA). Only 6 from 75 measured exposures exceeded this value. These exposures were measured on reactive site visits, in situations where a HSE inspector had reason to believe that exposure control was inadequate. No exposures in excess of the WEL were measured on the 2007 DRP visits at sites selected at random in an attempt to capture the typical situation within the industry.

The median exposure from 9 sites visited between 2004 and 2007 was 0.13 mg/m3. When HSE last systematically assessed the industry, in the mid to late 1990s, the median exposure was 0.3 mg/m3.

The rubber fume WEL of 0.6 mg/m3 was exceeded at two sites. Six measured exposures, 8% of the measurements taken, exceeded the WEL. In conclusion of the measured data the WEL of 0.6 mg/m3 could therefore be taken as 90th percentile as a worst case.

Although exposures are typically below the WEL, exposures are not being controlled as low as reasonably practicable (ALARP), as is the requirement for carcinogens under the COSHH regulations. Almost all sites visited had significant deficiencies related to the engineering controls used to control rubber fume exposures. Moulding presses without local exhaust ventilation (LEV) fitted were

frequently encountered. Where LEV was installed, deficiencies linked to design, use and maintenance were observed. The use of respiratory protective equipment (RPE) to control fume exposures was uncommon.