(first published November 2006, updated June 2009)

Even the simple task of washing dishes can have an impact on the environment.

For starters, many dishwashing detergents contain phosphate - it's a naturally occurring substance, but if too much of it gets into waterways, algae and phytoplankton feed on it and reproduce in massive numbers; causing an algal bloom.

One of the most dangerous blooms is created by blue-green algae, cyanobacteria. If large amounts are ingested, this can even kill humans.

Algal blooms block out sunlight and cause oxygen imbalances in a body of water; and as a result kill off other species.

While it's best to use a phosphate free detergent, depending on where you live and whether you wash by hand or use a dishwasher, it may be impractical or cost prohibitive to use phosphate free detergents.

This being the case, compare detergents for phosphate levels. A low phosphate level is considered to be around 1.6%, but you also need to compare how much detergent you need to use.

Other dish washing detergent nasties

Phosphate isn't the only concern. Dish washing detergents can contain a myriad of chemicals. Surfactants, stability and dispensing aids, fragrances and colors, mildness additives, preservatives and antibacterial agents are sometimes added. In some cases these might be naturally occurring substances, but often they won't. Some will be toxic to aquatic organisms and likely won't be filtered out at water treatment facilities.

To name all the possible chemicals used would be a mighty long list, so see my guide on identifying what's in a product.

What about the bottle?

Something else to check when buying detergents in plastic bottles is if the bottle can be recycled. If this aspect isn't clearly labeled on the bottle, look for the plastic resin code number that should be stamped on the bottle, usually in the middle of a triangle. You can learn what the various resin codes are in my article on recycling by the numbers.

Big is not always best

We're very much conditioned to believe that bigger is better. For example, if a small bottle of detergent is on offer at the same price as a larger bottle, we'll tend to opt for the latter. Buying in bulk can be good, but the thing to bear in mind with all detergents is the smaller bottle may be far more concentrated and actually be a better deal.

Choosing concentrated dish washing detergent products also means less packaging and less transport related emissions - less weight in shipping what is essentially just water.

Green dish washing detergents

The good news is that there are many more economical environmentally friendly dish washing detergents than there were just a few years ago, but their level of "greenness" will vary greatly. For example, a detergent may proclaim to be phosphate free, but the other ingredients will read like a laboratory shopping list - so be sure to study the labels before making a purchase decision and beware of greenwashing.

Quick dish washing tips

By the way - when hand washing dishes, you only need enough suds to cover the top of the water with a thin layer; anything over that is just overkill and aside from environmental concerns, you're just wasting money. Also, ensure you make the most of your bottle of detergent. When it seems empty, there's probably enough for a couple of washes left if you add a bit of warm water to the bottle and then shake! Little things like this multiplied by millions doing the same does help in a small way to minimize our negative impact on the environment.