N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine

Endpoint summary

Description of key information

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 (Health and Safety Executive) 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.
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.

Additional information

The monitoring results in detail:

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

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. In general a concentration of 3% of the substance in rubber products is assumed and therefore the expected exposure (0.6 mg/m3) can be reduced using a default factor of 0.2. This results in an expected exposure for the substance of 0.12 mg/m3.

This latter mentioned result is in good agreement with exposure data estimated with the program ECETOC TRA where low dustiness was assumed for the uses applied during the production of tyres and GRG and retreating and recycling processes. In conclusion the assumption of low dustiness for the mentioned uses seems to be justifiable.