Are there any downsides to having a coal deficiency if you've only used coal to build factories?

Yesterday I was playing Civilization V and lost the city containing my sole coal source. I had built factories in my other cities prior to this and as such I now ended up with a deficiency in coal. Now, from what I understand, units requiring coal have their efficiency reduced if your coal supply no longer can keep up, but is there a such penalty with factories?

In other words, are there any downsides to having a coal deficiency if you've only spent your coal on factories in Civilization V?

According to the Civilization 5 wiki page on coal:

Luckily, once you build a Factory, there doesn't seem to be any negative effect if you start running negative Coal resource.

It's hard to prove a negative, but the people maintaining the wiki have not found anything, so probably there is no downside.