^a Odds ratio calculated without consideration of possible confounders (ratio of exposed to unexposed cases divided by the ratio of exposed to unexposed controls).

^b 95% confidence intervals for the odds ratio calculated without consideration of possible confounders.

^c Includes all factors considered as potential confounders whether or not statistical adjustments were made for them.

^d VHCC, very high current configuration.

^e OHCC, ordinary high current configuration.

^f OLCC, ordinary low current configuration.

^g End pole, very low current configuration.