Anti-vaxxers can’t do math

October 25, 2011

A posting at a “newspaper” (I use the term loosely here) called the Canadian entitled ” America’s Toxic Flu shots: 250 times EPA mercury limit” has been getting a bit of attention (and ridicule) lately. The same article appears to be posted at another site under the name “Flu Shots Contain More than 250 Times the EPA’s Safety Limit for Mercury“, both by someone called Anthony Gucciardi. The article is riddled with factual errors, and actually identifies well-known quack Russel Blaylock as a “leading neurologist”. But without even going into all the factual errors, which have been pointed out elsewhere (such as here), the article has fundamental math errors that  make it even more laughable.

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Human health risks from oil pipeline spills

October 9, 2011

Oil pipelines have been in the news a lot this past year, between the proposed Keystone XL pipeline and various publicized oil spills. Potential human health effects of these spills are one of the concerns frequently raised, so I’m going to take a fairly high-level look at the potential risks here. Environmental effects are a separate topic that I’ll hopefully get to in the future.

First off, to have a human health risk, you have to have a few conditions met. The first is obviously that you have to have a potentially harmful chemical. Since any chemical, whether natural or synthetic, is potentially harmful at some dose, that one is kind of a given. The second condition is that chemical must get to where humans can be exposed. The third is that humans have to be exposed to enough of the chemical to have a potential for adverse health effects.

When oil is inside a pipeline there isn’t really any potential for exposure. So what happens when oil is released during a pipeline rupture?

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Mercury exposure from compact fluorescent lights

September 27, 2011

A commenter on a previous post asked about potential mercury exposure from broken compact fluorescent lights (CFLs). There are also various stories floating around the internet (such as this one) about the dangers of mercury in CFLs. So I thought I’d take the opportunity to look at how much mercury someone could be exposed to from a broken CFL, and whether there were any risks from that level of exposure.

A CFL typically contains about 4 mg of mercury (according to US EPA); a lot of newer CFLs contain 1 mg or less. I’ll look at the worst-case exposure, so let’s go with 4 mg of mercury in a bulb. In reality that mercury isn’t going to all be in the air right away – the evaporation rate of mercury is about 56 micrograms per hour per square centimetre – but figuring out the rate at which it enters the air requires assumptions about the area covered by the spilled mercury, temperature, pressure, etc. To keep things simple and to make sure I’m considering the absolute worst case, I’ll assume that all of that mercury instantly volatilizes.

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Cadmium – the new lead?

July 26, 2011

Health Canada has just proposed a limit on cadmium in children’s jewelry of 130 ppm (0.013%), which is lower than the limit for lead concentrations. This limit was imposed because after a limit was established for lead, manufacturers started using cadmium instead. Several pieces of jewelry tested over the last couple of years have been almost pure cadmium, but in most cases these items remained on the market because there is currently no regulatory mechanism by which Health Canada can force them to be recalled and the sellers refused to voluntarily recall them (and yet there is still a lot of political resistance to proposed regulations that would give Health Canada the power to force a recall…).

So what’s the concern with cadmium, and is it really more toxic than lead? Read on…

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Classification of formaldehyde as a human carcinogen

June 20, 2011

There have been a few reports in the news recently about how the US government has added formaldehyde to their list of substances known to cause cancer in humans. This doesn’t really come as a surprise – the International Agency for Research on Cancer (IARC), for example, already classifies formaldehyde as a confirmed human carcinogen. But since there’s some media attention on the subject right now, and since formaldehyde exposure can occur from a variety of sources, including many consumer products, it seems a good time to look at what this classification means for the general public.

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Methylmercury and fish consumption

June 9, 2011

After a bit of a break, I’m getting back to my series of posts related to mercury. This time I’ll focus on methylmercury, which is generally considered to be one of the “nastier” forms, since it is relatively toxic (primarily neurotoxicity, but also believed to cause cardiovascular and reproductive toxicity at high doses) and also bioaccumulates in animals. Since the main source of methylmercury exposure is food, and in particular fish, I’ll look at how the amount of mercury in fish relates to potential effects on humans.

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Health effects from chemical exposures – not just a modern phenomenon

May 29, 2011

When we think about exposures to chemicals causing adverse effects on human health, there is a tendency to view this as a product of modern industrial societies. To some extent this is true – there are certainly potentially hazardous chemicals we are exposed to as a result of our lifestyles, such as volatile chemicals in paints and solvents, the gasoline used to fuel our vehicles, and products of the combustion of tobacco. Most of the instances where we can clearly associate an adverse health effect with a particular chemical exposure are from workers in factories and chemical plants.

However, a new paper by Sebastian Wärmländer and colleagues examines a much older case of exposure to harmful chemicals – specifically aboriginal populations in California starting around 10,000 years ago exposed to polycylic aromatic hydrocarbons (PAH).

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