Learn about the Health Threat of EMFs from Electric Cars
Biên tập viên: Trần Tiến Phong
Đánh giá: Trần Trà My, Trần Phương Phương
There has been a fair amount of buzz on the Internet speculating whether or not the emergence of electric vehicles (hybrids, battery electrics, etc.) will lead to a rash of sickness and death from electromagnetic fields (EMFs). These concerns are largely unfounded based on simple examination of the facts on how EMFs and electric cars themselves operate.
The first thing to understand is how EMFs are created and how their resulting radiation (called EMR) affects humans. There are many types of EMF and most of them create some kind of EMR.1 EMRs come in two types: ionizing and non-ionizing. For electric vehicles, the non-ionizing types are the ones of note. Ionizing EMF radiation comes from X-rays and other high-frequency emissions, not from standard electrical devices.
The two types of electricity that we use (alternating and direct currents, or AC / DC) have different properties in the types of EMF they create. AC creates much larger EMFs and much more EMR than does DC power.
The field from an overhead power line carrying AC can be quite large while the field from a battery-powered radio is not likely to even extend beyond the radio's casing. The difference is both the intensity and the type of EMF being emitted. The AC lines are giving off intermittent frequency or vibratory EMR while the battery-powered radio gives off static EMR, which is considered less dangerous.
Few studies in electric vehicle EMFs have been done and those that have are either more than a decade old or are not conclusive. The most-often cited study was done in 1999 by Electric Research of State College, Penn.2 for the Department of Transportation. The study does show that electric commuter trains are extreme emitters of EMFs, but that even the electric cars and trucks of a decade ago were not much worse than standard gasoline vehicles.
The question of how much EMR an electric vehicle creates was recently renewed when a New York Times article reported on a woman's assertion that her hybrid was causing her to pass out.3 Her story had little credence and is not backed up by facts. Every manufacturer of electric or hybrid vehicles (including the one she was driving) shield their wiring thickly. This is not so much for passenger safety (there are no U.S. safety standards for EMF/EMR) as it is to keep the EMFs they might create from interfering with other electronics such as cell phones or radios. The fields are small to start with - it turns out - thanks to the fact the cars utilize direct current (DC) almost exclusively.
The Internet is abounding with stories about how much or how little EMFs are given off by this-or-that electric vehicle. What is rarely given is what type of Gauss meter was used to measure the EMF. This plays a big part in how accurate and useful the data being collected is. Usually, these tests are likely being done with the EMF readers that professional electricians use for commercial and residential buildings. These readers are the most common, but they are also the least accurate for answering the question of whether the field is harmful since they do not give frequency-specific information, only an overall field reading. Other sources of EMFs around the vehicle (ambient sources) are also rarely accounted for, which is another problem.
So while EMFs are definitely a concern,4 it's unlikely that your biggest worries will come from electric and hybrid cars. Your cell phone, overhead power lines, and other sources of more intermittent and higher-frequency EMRs are a lot more problematic.