
They have been hailed as the environmentally-friendly solution to getting around towns and cities.

But new research has found electric cars have an overall impact on pollution that may be worse than gas-guzzling vehicles.

The study looked at US vehicle emissions on a county-level to map where gas cars and electric vehicles cause the most damage to the environment.

It found that in the east of the US, the impact of charging up EVs overnight does more harm to the environment than going to the petrol station.

A study has found electric cars (right) have an impact on pollution that may be worse than gas-guzzling (left) vehicles. The study looked at US vehicle emissions on a county-level to map where gas cars and electric vehicles cause the most damage. In some areas, shown in red on the right, the impact of charging up EVs overnight does more harm to the environment than going to the petrol station

'What we find is that the benefits are substantially different depending on where you are in the country,' study co-author Stephen Holland of the University of North Carolina, told CityLab.

The real big take-home message is: location, location, location.'

The study, by the National Bureau of Economic Research, looked at five major pollutants: carbon (CO2), sulphur dioxide (SO2), nitrogen (NOx), particulate matter (PM 2.5), and volatile organic compounds (VOCs).

They took into account 11 different 2014 models of EVs, as well as the 'closest substitute' gas car.

For gas cars, the researchers studying the car's fuel-efficiency rating, the average wind patterns in an area and other environmental factors, such as farmland.

Pictured on the right are estimated electric vehicle subsidies across the US, and on the left, suggested electric vehicle subsidies by state. The US government currently pays $7,500 for every electric car purchased — a subsidy that the study authors say the US should scrap

SELF-DRIVING TAXIS COULD CUT POLLUTION, SAYS STUDY Imagine a fleet of driverless taxis roaming your city, ready to pick you up at a moment’s notice. Scientists claim it may be only a matter of time before it becomes reality. nd according to a new study from Lawrence Berkeley National Laboratory, such a system would both be cost-effective and reduce per-mile emissions of greenhouse gases. The study found that the per-mile greenhouse gas emissions of an electric vehicle deployed as a self-driving, or autonomous, taxi in 2030 would be 63 to 82 per cent lower than a projected 2030 hybrid vehicle driven as a privately owned car and 90 per cent lower than a 2014 gasoline-powered private vehicle. Advertisement

This provided researchers with the total emissions of driving a certain gas car one mile in a given U.S. county.

For EVs, researchers analysed at how much electricity each car drew from a regional grid and the hourly emissions profiles for the five pollutants at 1,486 power plants across the U.S.

This gave them a figure for the amount of environmental damage that car produced at the power plant, according to a report in CityLab.

Overall the results showed that the west of the US is a lot cleaner than the east when it comes to driving EVs.

In monetary terms, electric cars are about half-a-cent worse per mile for the environment than gas-powered cars.

With gas cars, the worst damage, which is shown on the map in red, took place in highly-populated urban areas such as New York.

Environmental damage for EVs appears to be worse in the Midwest and Northeast, where the electricity grid tends to rely on coal power plants.

In places like LA, EVs produce less environmental damage because the city's air shed traps pollutants from gas cars.

Here, electric cars are 3.3 cents per mile better for the environment than gas-powered vehicles. Outside of populated areas, electric cars are generally 1.5 cents per mile worse than gas-powered.

The federal government currently pays $7,500 for every electric car purchased — a subsidy that the study authors say the US should scrap.

In monetary terms, electric cars are about half-a-cent worse per mile for the environment than gas-powered cars. In places like LA, EVs produce less environmental damage because the city's air shed traps pollutants from gas cars

'Because electric vehicles, on average, generate greater environmental externalities than gasoline vehicles, the current federal policy has greater deadweight loss than the no-subsidy policy,' the authors write.

'It's kind of hard to beat gasoline' for public and environmental health, said co-author Julian Marshall, an engineering professor at the University of Minnesota.

'A lot of the technologies that we think of as being clean ... are not better than gasoline.'

The key is where the source of the electricity all-electric cars.

If it comes from coal, electric cars produce 3.6 times more soot and smog deaths than gas, because of the pollution made in generating the electricity, according to a separate study published in December by the Carnegie Institution for Science.

The states with the highest percentage of electricity coming from coal, according to the Department of Energy, are West Virginia, Wyoming, Ohio, North Dakota, and Illinois.

But if the power supply comes from natural gas, the all-electric car produces half as many air pollution health problems as gas-powered cars do.