On the vog, the offending volcano is on the east side and the trades, which come from the east to the west, blow it around Mauna Loa, primarily to the south, and as mentioned earlier it tends to eddy on the west side of the island. HOVE to Kealakekua, and to some extent Kailua, tend to be the hotspots. Kona winds, which I believe come primarily from the west, are most common in the late winter and spring, trades tend to be more common in the other parts of the year (last I heard we experience trades roughly 230 days a year). I think the vog the other islands experience in Kona winds is from the plume heading waaaay out to the west in normal trade activity coming back at them. A couple days of Kona winds, or south winds, or north winds, does wonders in most of Kona proper, clearing out the skies. We've had some wonderfully clear days this winter. After multiple days of Kona winds, Hilo can have vog tremedously badly. Except for a period of very heavy vog in the spring of '08 or so, with air quality alerts in HOVE on one day, the only air quality alerts I've heard of on the island have been in the Hilo area when there are west winds.
The vog effects different people different. My wife had a lot of allergy problems in Oregon, I had few. She has had limited issues with the vog, while I notice it more when it's really thick. I was listening to an am radio show a few years back and it talked about a study that the county of Hawaii was doing on school aged kids and the vog that started back about 10 years ago. They were tracking vog and respiratory problems with kids long term. 5-6 years into the study they found that the district with the most respiratory problems in kids they were tracking was Hamakua, which is pretty much the district that by far sees the least vog. Turns out it has the highest population of smoking parents though. The study is ongoing, and I think was following kids that were early primary school ages at the time, and may have different results now that those kids are older. I haven't heard a follow up.
There's no telling if the vog will effect you 'til you get here, many many tourists I talk with don't know the difference between vog and the clouds that build up on the mountains from convection activity on a daily basis. Residents seemed to become more sensitized to it as time passes, but still the vast majority of the residents here are unconcerned. I could see on the other islands if you are used to the lack of vog, voggy days can be depressing.... sort of like how extended periods of rain is to us in Kona and Kohala, and might likely trigger off an allergic response if they haven't experienced it and aren"t acclimated to it.
