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It's hard to put a straight number on it, other than that "it will most likely reduce the negative effects".

A standardized HEPA filter removes 99.97% of particles down to PM0.3. How much it cleans the air in the room in the end depends on many factors, but in a small room and a decent filter you can expect a significant reduction in pollution.

So yes, if you want less pollution, a HEPA filter will deliver it in a theoretical range of zero to 99.97% purification, depending on the variable factors of room size, air circulation, purifier air flow and so forth.

A properly sized purifier will circulate all air in a room several times per hour, so in practice you can expect a good cleanup of particulates (perhaps around 80%) in a fairly short period of time (less than an hour).

Btw. just for curiosity, there is a difference in the source of radiation as it pertains to how dangerous it is.

Banana (potassium) radiation is mostly harmless to humans. Nuclear weapon or reactor radiation (for example caesium) is not.

The Banana equivalent dose is therefore a bit of a misleading term, and I have sometimes seen it used to dismiss other more harmful radiation sources as harmless, because of this incorrect banana comparison.

http://www.washingtonsblog.com/2013/04/fake-science-alert-fu...

Here is an example of using the banana comparison in an incorrect manner:

http://www.forbes.com/sites/timworstall/2013/08/10/the-fukus...

Am I? The Nature article explicitly states that the shift in diagnosis criteria does not fully explain the increase in numbers.

"Shifting diagnoses and heightened awareness explain only part of the apparent rise in autism. Scientists are struggling to explain the rest."

http://www.nature.com/news/2011/111102/full/479022a.html

I don't quite buy that autism will be shown to be genetic. I think it's an environmental factor. The rate of increase in autism is pretty much exponential:

http://www.nature.com/news/2011/111102/full/479022a/box/1.ht...

Now that's a very scary chart if you start to project that curve into the future.

Here's another one. Not saying this is the cause, but it is a cause for concern. We have many similar patterns of environmental factors increasing with autism prevalence, which makes the likelihood of it being environmental stronger than something else.

http://images.medicaldaily.com/sites/medicaldaily.com/files/...

For example it took a long time to figure out that lead in gasoline could lead to cognitive decline. BPA and phtalates is another recent discovery, which cause hormone distruption.

What else do we have today that is yet to be figured out, and what is the likelihood that we have something similar brewing that we do not yet know about.

Study report is here: http://biorxiv.org/content/biorxiv/early/2016/05/26/055699.f...

The results do not seem all that convincing to me, even though the authors seem to be saying that the results are significant.

But it's not like a significant percentage got tumors while the controls did not. The differences are in the order of a few percent. Probably worth a closer look, but does not seem to me you can draw some major conclusion from this.

Unfortunately the human factor is exactly the problem with these types of systems. I don't think humans can ever be considered to be safe stewards of anything where a seemingly remote cascade event can wipe out life on the planet.

Look at the disaster of Long-Term Capital Management from the financial industry as an example, where a presumed ten sigma event almost wiped out the whole western financial system.

http://epicureandealmaker.blogspot.fi/2007/05/11000000000000...

These nuclear reactors are built with the same underlying principles and risk-management profiles. There's always the element of human error; you can't over-engineer something you did not foresee. In addition to that you have the enormous profit incentives from running nuclear power. These incentives can overwhelm the incentives for safety, or lead to disregard of warnings where profit potential would be compromised if warnings were attended to.

It's human, therefore it's hard to ever sleep completely sound knowing that these constructions are running on the planet.

Fukushima didn't just happen because one mistake was made either. It happened because a long string of mistakes and disregard of safety happened. Want to bet it doesn't happen again? It's hard to bet against human nature...

http://carnegieendowment.org/files/fukushima.pdf