Smog (fog and air-borne, man-made pollutants, combined) make a heavier burden (electrically) for insulators than most people think. The arid climate in Southern California (especially) causes whatever "crap" from pollution to condense upon the many thousands of multipart pintype insulators (owned by the Los Angeles Department of Water and Power, the largest municipally-owned electric utility in the US, FYI). Complemented by the Southern California Edison (SCE) who also has customers within some of the Los Angeles basin area communities.

Electrical energy is "transported" from distant locations to the LA area customers, mostly. Line losses primarily accumulate upon insulators on their 44kv networks and a lot of this is happens due to electrical "tracking" ground losses. DWP has had a continuing program to replace older insulators within their 44kv sub-transmission system upon retirement. Existing insulators (suspension strings and multipart insulators) seen throughout DWP territory are continually kept clean via washing. In this photo a truck crew is washing insulators on a circuit. Nowadays helicopters do the same thing using high-pressure washing without having to switch circuits for maintenence...and they do it a lot faster than the pole-to-pole truck method provided by autolit.