EAnna wrote
Sea salt and rock salt include nitrates, nitrites and metal oxides.
It seems that nitrate (or nitrite) concentrations in seawater are more or less negligible; in the range of 10-80 ppb (parts per billion = .001 ppm). Multiplying by 30 to get the amount in sea salt puts it roughly at 1-2 ppm, whereas commercial curing salt contains 6000 ppm (sodium) nitrite.
So really nothing to worrying about EAnna your tap water could also contain nitrates ...
Ground water supplies naturally contain a variety of chemical compounds, including nitrate. Most commonly nitrates may be found where the region local to the groundwater has had significant plant decay underground. Nitrates are created as a part of the decaying process, and are able to move relatively quickly and easily through soil, owing to how soluble they are.
Kind regards
Stephen x
If all else fails ......
Read the instructions !!!!