Table 4.

Comparison of WAMs for total metalworking aerosol by decade, industry, operation and fluid type

Decade	Industry type	Operation type	Fluid type	No. of measurements	WAM (mg m−3)	SD (mg m−3)	Multiple mean comparison testa	P-valueb
<1970s	All	All	All	311	5.36	4.28	a	<0.001
1970s	All	All	All	874	2.52	1.76	b
1980s	All	All	All	1085	1.21	0.93	c
1990s	All	All	All	6002	0.50	0.31	c
2000s	All	All	All	1107	0.55	0.19	c
All	Auto	All	All	1775	1.47	1.10	a	<0.001
All	Auto part	All	All	1126	1.83	3.16	a
All	Small jobs	All	All	4751	0.68	0.84	b
All	All	Grinding	All	1005	1.75	1.84	a	0.002
All	All	Machining	All	3583	0.95	1.71	b
All	All	All	Straight	1406	1.49	1.45	a	0.017
All	All	All	Soluble	2233	1.08	1.50	NS
All	All	All	Synthetic	321	0.52	0.14	b
All	All	All	Semisynthetic	551	0.50	0.20	b
All	All	All	Water miscible	3105	0.92	1.30	b
<1970s	Auto part	All	All	63	10.26	7.60	NS	NS
<1970s	Small jobs	All	All (straight)	248	4.11	0.95
<1970s	All	Grinding	All	17	3.05	NA	NS	NS
<1970s	All	Machining	All	46	12.92	7.08
<1970s	All	All	Straight	257	4.01	1.04	NS	NS
<1970s	All	All	Soluble	17	3.05	NA
1970s	Auto	All	All	627	2.11	1.00	NS	NS
1970s	Auto part	All	All	211	4.09	2.56
1970s	All	Grinding	All	259	3.80	2.62	NS	NS
1970s	All	Machining	All	369	1.86	0.99
1970s	All	All	Straight	112	1.86	1.44	a	0.062
1970s	All	All	Soluble	281	4.07	2.05	b
1980s	Auto	All	All	988	1.15	0.93	NS	NS
1980s	Auto part	All (machining)	All (soluble)	92	1.73	0.92
1980s	All	Grinding	All	161	1.94	0.73	NS	NS
1980s	All	Machining	All	653	1.40	0.91
1980s	All	All	Straight	176	1.40	1.23	NS	NS
1980s	All	All	Soluble	387	1.29	0.98
1980s	All	All	Synthetic	25	0.66	0.09
1980s	All	All	Semisynthetic	16	0.71	NA
1990s	Auto	All	All	127	0.98	1.46	a	0.092
1990s	Small jobs	All	All	4503	0.49	0.16	b
1990s	All	Grinding	All	334	0.77	0.17	a	0.006
1990s	All	Machining	All	2472	0.47	0.40	b
1990s	All	All	Straight	845	0.71	0.22	a
1990s	All	All	Soluble	1382	0.47	0.55	b
1990s	All	All	Synthetic	296	0.51	0.14	NS
1990s	All	All	Semisynthetic	326	0.36	0.09	b
2000s	Auto	All (machining)	All (semisynthetic)	33	0.70	NA	NS	NS
2000s	Auto part	All	All	760	0.51	0.15
2000s	All	Grinding	All	234	0.66	0.16	NS	NS
2000s	All	Machining	All	43	0.63	0.17
2000s	All	All	Straight	16	0.61	NA	NS	0.005
2000s	All	All	Soluble	166	0.42	0.12	a
2000s	All	All	Semisynthetic	209	0.70	0.13	b
All	All	All	All	9379	0.94	1.41

NA: not applicable because number of studies = 1. The number of measurements across subcategories may not equal the total number of measurements for any particular category because means are not presented when information on a subcategory was not provided.

^aMultiple mean comparison t-test; different letters indicate significant differences, ‘NS’ indicates no statistically significant differences with any other groups.

^bANOVA (dependent variable = log-transformed value).