Human health risks from oil pipeline spills

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?

When oil is released from a pipeline, it spreads out in the surrounding soil. How far it goes depends on the size of the rupture and how much time passes before it is noticed, the type of oil in the pipeline, and the geology. Most underground spills don’t go a huge distance, but can travel over tens of metres in some cases. Surface spills can travel further since they aren’t as confined, and spills into a water body can potentially travel fairly long distances.

When oil is present in soil, there are basically three things that can happen to it over the short term. The first is being physically bound to the soil; most of the heavier hydrocarbons end up in this state. The second is to enter a vapour form and become airborne; this really only happens to significant extents for fairly light hydrocarbons that might be found in light crude oil, for example. The third is to be dissolved into water between the soil pores, which could eventually move towards the water table – again mostly for light hydrocarbons. Oil spilled on the surface or in water is more likely to end up in vapour or dissolved phases than an underground spill.

So what is the potential for human exposure? The hydrocarbons bound to the soil are pretty much going to stay put, possibly degrading slowly over time (or until remediated); really the only potential for exposure is if a person comes into direct contact with the contaminated soils near the pipeline, and even then risks aren’t generally that high except in the case of something like children playing in the contaminated soil. There is also potential exposure if food crops are grown directly in the contaminated soil, though most petroleum hydrocarbons don’t bioaccumulate to a huge extent since they’re metabolized. Overall there are some localized risks, but once the contamination is identified they can generally be managed fairly readily.

Hydrocarbon compounds in the vapour phase are obviously more mobile, but at the same time they tend to break down fairly quickly in air. The biggest concerns are compounds like benzene which can be present at significant concentrations in light oils, but between the degradation in air, dilution due to air movement, and limited quantities of the volatile compounds, risks are fairly localized and short-term, unless there is a building such as a house on top of or within a few metres of the contamination (which wouldn’t be allowed in most places). Heavier oil mixtures or bitumen don’t have a lot of the light-end hydrocarbons that can enter air.

The portion that is dissolved in soil pore water is probably the portion with the biggest human health risk if it can enter an aquifer used for drinking water. Again this is really only an issue for light-end hydrocarbons; heavier hydrocarbons don’t really move very far and aren’t very soluble. This is really only an issue if there is a shallow aquifer used for drinking water that isn’t geologically isolated from the oil contamination. One of the concerns raised about the Keystone XL pipeline is the potential for impacts to the Ogallala Aquifer, which according to the Wikipedia entry ranges from 30 m to 122 m below the soil surface. I’ve seen soil and groundwater investigations from a lot of oil spills, and even spills of very light oil mixtures don’t travel more than a few metres downward. In the case of the Keystone pipeline the product would be bitumen (which is very insoluble and immobile), the shallowest depth is 30 m and surface recharge to the aquifer is known to be very slow, so there isn’t really any possibility of a pipeline break resulting in bitumen contaminating the aquifer. There are some more volatile compounds used to dilute bitumen for transport, but these compounds are more volatile and have a fairly short environmental life; vertical migration velocities are not high enough for these compounds to travel downwards 30 m before they degrade unless there’s some sort of conduit for them; in my experience it’s fairly rare for them to be found more than about 5 or 6 m below ground surface from a pipeline spill.

The biggest risks to human health occur when a pipeline release occurs into a surface water body, particularly if that surface water body is used as a source of drinking water or for recreational use, since in that case the oil is potentially released directly into the water. This is where efforts should be focused in my opinion – reducing unnecessary surface water crossings, and ensuring that when pipelines do cross surface water bodies that protective measures are taken and proper monitoring is in place.

5 Responses to Human health risks from oil pipeline spills

  1. Mahdi says:

    pretty good and useful information.

  2. Mahdi says:

    can you give some more information on soil part?

  3. James says:

    I don’t buy the sugar coated version you were paid to say here. You are looking at it as if that’s all there is to it. You should do the PR malarkey for Monsanto too while you’re at it – or for fluoride, aspartame or fracking too! :/ Sadly most people don’t do their own research though. Do a search on a trustworthy and extensive search engine. But don’t just look at the first link of a skewed or spin doctor report on it either. Keep looking until you find some UNBIASED report given by a concerned scientist or other professional on the subject. They are lying to you so they can get away with making trillions of dollars at the expense of the environment and all life on planet earth. Whether it’s oil, gas, tar, pipelines or fracking there are risks ‘they’ will not tell you about. In fact they will distort the facts or even outright lie to you in order to keep making their dirty money that is not just oil stained – but also BLOOD STAINED MONEY!

  4. Great post! Been reading a lot about avoiding exposure to chemicals like this. Thanks for the info here!

  5. cctldlist says:

    Whats up this is kinda of off topic but I was wanting to
    know if blogs use WYSIWYG editors or if you have to manually code with HTML.
    I’m starting a blog soon but have no coding
    skills so I wanted to get advice from someone with experience.
    Any help would be greatly appreciated!

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