"Some of the intimate conversations I have with women is just extraordinary. You're helping them with their babies ... or they just want to talk about the child they lost or the husband they lost.
"You can't walk away from that and just park that on the shelf as just another day in your journalistic career. There's a genuine need and it is the humanitarian crisis of my time."
Retimanu, whose smooth voice is well-known to listeners, has lost more than 30kg over the last few years and is looking forward to pushing herself for a good cause next Sunday.
The group will visit refugee camps on the Syrian border a day before the 42km marathon. It is an experience Retimanu says will be emotional.
"If we think we've got problems - well we don't, compared to these people. I'm glad we're going a day before the marathon, because that will inspire and motivate everyone."
The Forgotten Millions campaign kicked off in March and raised $436,000. Last month it was relaunched after poignant images and stories of refugees fleeing to Europe emerged.
New Zealanders donated another $645,000 - taking the combined total of donations to just over $1 million.
A gala auction dinner was held shortly afterwards and Prime Minister John Key matched the money raised, taking the total past the $2 million mark. Today, a total of $2.75 million has been raised for the cause.
Smalley called on Kiwis to keep giving to a people who will continue to endure this plight for a long time.
"They're not refugee camps you'd see, say, in Africa, when there's a famine or a drought. Because when something like that happens, the aid agencies know - they can say: 'In Ethiopia, the rains didn't come, the crops aren't going to come and so in two months' time, we're going to have a lot of hungry people'. So they start setting up camps.
"But when you've got a humanitarian crisis that's been triggered by a conflict, you can't predict that. Bombs are going off and people are running."
•To sponsor a runner or to donate visit: tinyurl.com/prvewfp
Beirut Marathon
•When: Sunday, November 8.
•Where: Beirut, capital of Lebanon.
•History: Now in its 13th year.