Do Newspapers add heavy metal to soil when used in a mulch or added as ashes?
A few years ago there were many warnings put out about using coloured paper in the garden. The brilliant colours were produced using various metal oxides. Cadmium and Lead were often used for Reds but a highly toxic selection could be found in the inks. Black was obtained from carbon and is not toxic.
The main problem was not garden contamination but rather human contact from ink rubbing off on readers hands. Of course printers and newspaper handlers were being exposed to much higher levels of these heavy metals.
Another issue was the medium in which the black and other colours were carried.
Ink can be made to dry on paper in several ways. It can have solvents and varnishes that evaporate leaving a solid ink mark that does not smear or stick to the other pages. This is used in books and other high quality printing.
Another method of getting the ink to stick to paper is to mix the pigments that make up the ink in an oil. When the oil and pigment ink is deposited on porous paper, the oil is absorbed down taking some of the pigment with it. In this process the ink does not harden in the same way and always remain somewhat soft and can be smeared. This is the process used to print on newsprint.
The oils used in the past were mineral oils derived from the petrochemical processes.
Do modern newspapers contain heavy metals.
When the problem was recognized there was public demands for safer inks and Governments in industrialized countries recognized the problem and put regulations in place to remove the toxic metals from the ink. Newspapers and printers were forced to replace the colour with less toxic alternatives, (and many were happy to comply.)
Modern colours are produced using synthetic pigments, not metallic oxides so that newspaper mulches and ashes do not significantly contribute to buildup of heavy metals in the soil.
Some inks still contain heavy metals but these are used on glossy papers not newsprint. It is no longer even common.
The benefits of using newspaper mulch are far greater than any danger of contamination due to heavy metals.
How about the carrier oils, have they been replaced
The very small amount of oil based carrier that is still in use in some inks has not been enough to cause any danger or chance of accumulation. The oil has now been replaced by vegetable oils and is now almost all SOY based anyway.
Fortunately petroleum based oils do eventually break down and do not accumulate in the soil.
Of course if you are only worried about ashes then there is no issue of oil remaining in the ashes after burning.
Contamination can come from many places
We live in a chemical soup and contamination can come from many places. I remember seeing a documentary on Salmon culture. Various methods of production were monitored for contamination, particularly by mercury. Much to everyone's surprise the organicly produced and naturally caught fish had a heavier load of mercury than some of the non organic farmed fish. The salmon's natural diet of wild fish and the organicly farmed diet containing wild fish meal contained mercury while the more "processed" diet of some of the regular farmed fish included less natural fish meal and included a step to filter out the mercury. Organic is not always better.
By adding fish meal, fish and marine compost, blood meal and many other naturally based fertilizers, organic farmers can be adding heavy metals. Air borne Pollutants can settle in the water and on the soil so it is very difficult to avoid completely. Oil can be added to the soil from tractors, run off to streams from roads, oiled shovels and spades and an infinite number of other places.
IS Newspaper Mulch and Ash Safe?
Yes it is. Avoid glossy coloured paper supplements, they still sometimes contain nasty stuff, but regular and coloured newspaper is safe.
You are more likely to get contamination from dirty run off or air borne dirt than from newspapers.
Keep in mind that ashes should not be added in large quantities. They change the PH of the soil.