Table 2

Statistical interactions expressed as RIRRs representing an estimate of the ratio of the individual IRRs for the defined groups (A–J) for the stated time periods as defined in the methods

ID	Control of isocyanate exposure in MVR	Time periods	Type of ill-health	Time periods compared	A. All workers: spray paint vs other agent		B. MVR vs other industries (all agents)		C. Motor vehicle manufacture vs other industries (all agents)
ID	Control of isocyanate exposure in MVR	Time periods	Type of ill-health	Time periods compared	RIRR	95% CIs	RIRR	95% CIs	RIRR	95% CIs
1	HSE intervention (2004–2007)	time1=2001–2003 time2=2004–2007 time3=2008–2010	SLRD	time2/time1	1.21	0.74 to 1.97	0.34	0.12 to 0.95	1.38	0.92 to 2.07
			SLRD	time3/time1	1.03	0.56 to 1.87	1.67	0.78 to 3.61	1.05	0.64 to 1.70
			Asthma	time2/time1	1.26	0.75 to 2.09	0.39	0.14 to 1.12	1.26	0.83 to 1.92
			Asthma	time3/time1	1.29	0.70 to 2.40	1.85	0.80 to 4.28	0.93	0.55 to 1.58

ID	Craft bakeries: exposure to flour dust and enzymes in improvers	Time periods	Type of ill-health	Time periods compared	D. All workers: flour vs other agents		E. Food industry: flour vs other agents		F. Attributed to flour in bakers: retail vs industrial
ID		Time periods	Type of ill-health	Time periods compared	RIRR	95% CIs	RIRR	95% CIs	RIRR	95% CIs

2a	Introduction of a MEL (April 2001) Introduction of a WEL (25 April 2005) HSE inspection pack (2006–2008)	time1=May 1999–Apr 2001 time2=May 2001–Apr 2003 time3=May 2003–Apr 2005 time4=May 2005–2008 time5=2009–2010	SLRD	time2/time1	1.54	0.89 to 2.68	1.60	0.66 to 3.86	8.45	2.36 to 30.33
				time3/time1	2.09	1.22 to 3.57	2.05	0.85 to 4.92	3.63	1.17 to 11.20
				time4/time1	2.35	1.42 to 3.89	2.30	1.00 to 5.31	2.50	0.88 to 7.17
				time5/time1	3.03	1.69 to 5.43	4.69	1.49 to 14.74	5.49	1.65 to 18.23
			Asthma	time2/time1	1.37	0.76 to 2.47	1.37	0.54 to 3.48	7.03	1.85 to 26.76
				time3/time1	1.95	1.11 to 3.42	1.90	0.75 to 4.77	3.12	0.95 to 10.27
				time4/time1	2.24	1.33 to 3.79	2.32	0.96 to 5.60	2.50	0.83 to 7.57
				time5/time1	2.90	1.55 to 5.43	5.36	1.35 to 21.23	5.79	1.56 to 21.40

2b	Introduction of a WEL (25 April 2005) HSE inspection pack (2006–2008)	time3=May 2003–Apr 2005 time4=May 2005–2008 time5=2009–2010	SLRD	time4/time3	1.12	0.73 to 1.74	1.13	0.51 to 2.48	0.69	0.30 to 1.59
				time5/time3	1.45	0.86 to 2.45	2.29	0.75 to 6.96	1.52	0.55 to 4.16
				time5/time4	1.29	0.79 to 2.10	2.03	0.69 to 5.99	2.19	0.87 to 5.52
			Asthma	time4/time3	1.15	0.72 to 1.84	1.22	0.52 to 2.88	0.80	0.33 to 1.93
				time5/time3	1.49	0.83 to 2.66	2.83	0.73 to 11.03	1.85	0.60 to 5.68
				time5/time4	1.29	0.75 to 2.23	2.32	0.61 to 8.79	2.31	0.82 to 6.50

ID	Controlling inhalation exposure to metalworking fluids	Time periods	Type of ill-health	Time periods compared	G. All workers: MWF vs other agents		H. All workers: MWF vs other agents (excluding one reporter*)
ID	Controlling inhalation exposure to metalworking fluids	Time periods	Type of ill-health	Time periods compared	RIRR	95% CIs	RIRR	95% CIs

3	HSE inspection pack and removal of MEL without replacement with WEL (2005–2006)	time1=2002–2004 time2=2005–2006 time3=2007–2008	SLRD	time2/time1	2.20	1.19 to 4.06	2.69	0.87 to 8.33
			SLRD	time3/time1	2.02	1.05 to 3.89	4.61	1.55 to 13.72
			Asthma	time2/time1	2.20	1.10 to 4.43	1.59	0.39 to 6.44
			Asthma	time3/time1	1.12	0.47 to 2.70	2.06	0.51 to 8.37

ID	Controlling inhalation exposure to rosin based solder fume	Time periods	Type of ill-health	Time periods compared	I. All workers: solder vs other agents
ID	Controlling inhalation exposure to rosin based solder fume	Time periods	Type of ill-health	Time periods compared	RIRR	95% CIs

4	Introduction MEL (March 1999) Introduction of WEL (25 April 2005) HSE inspection pack (2007–2008)	time1=Jan 1996–Mar 1999 time2=Apr 1999–May 2002 time3=Jun 2002–Apr 2005 time4=May 2005–Dec 2008 time5=Jan 2009–Dec 2010	SLRD	time2/time1	0.96	0.58–1.59
				time3/time1	0.64	0.35 to 1.16
				time4/time1	0.45	0.23 to 0.88
				time5/time1	0.69	0.30 to 1.57
			Asthma	time2/time1	0.92	0.55 to 1.55
				time3/time1	0.64	0.34 to 1.19
				time4/time1	0.48	0.25 to 0.94
				time5/time1	0.73	0.30 to 1.77

ID	Wood dust: Controlling inhalation exposure	Time periods	Type of ill-health	Time periods compared	J. All workers: wood dust vs other agents
ID	Wood dust: Controlling inhalation exposure	Time periods	Type of ill-health	Time periods compared	RIRR	95% CIs

5	Introduction of WEL (25 April 2005) HSE inspection pack (2002–2007)	time1=2002–2004 time2=2005–2007 time3=2008–2010	SLRD	time2/time1	0.89	0.42 to 1.87
			SLRD	time3/time1	1.18	0.56 to 2.48
			Asthma	time2/time1	1.04	0.48 to 2.26
			Asthma	time3/time1	1.31	0.58 to 2.97

The RIRR can be considered an estimate of the magnitude of the difference in the change in incidence between the groups over the defined time periods.
*Analysis G was repeated excluding the reporter investigating the outbreak of respiratory disease related to MWF.16 ,17
HSE, UK Health and Safety Executive; MEL, maximum exposure limit; MWF, metalworking fluid; RIRR, ratio of incidence rate ratios or interaction term; SLRD, short latency respiratory disease (includes asthma, allergic alveolitis, rhinitis, inhalation accidents); WEL, workplace exposure limit.