The substance at the centre of an incident near Ludchurch on Sunday has been identified as consisting of mainly cereal grain dust from animal feed.
The powder, which sparked a major safety scare, was left in the gateway to a field belonging to Killanow Farm.
Two police officers who attended the scene were later treated for sore throats, headaches and sickness.
The substance was later removed and sent to the public analyst in Cardiff for identification.
Tests have confirmed that the very small spiky nature of the dust from the grain hairs would act as an irritant to the skin, eyes and lungs.
There may also be traces of a powder which is a preservative used in some animal feedstuffs and also in some foods for human consumption.
This is based on propionic acid and direct exposure to a significant concentration of this substance could give rise to a feeling of nausea.
Pembrokeshire County Council's public protection division has now requested the laboratory in Cardiff to analyse the substance for propionic acid.
Said Richard Brown, the council's senior pollution control officer: "Regardless of the latest results, we can positively say, based on the laboratory analysis, there are no long-term health risks to either humans or livestock."
Since the incident, public health doctor, Kiran Humphrys, has issued the following advice to members of the public:
"If any members of the public were walking in the vicinity of Little Kings Park, Ludchurch, between Saturday evening and Sunday and are experiencing any symptoms such as headaches, sore throats, nausea or skin irritation, they are advised to wash the clothing and footwear that they were wearing at the time and if unable to do so immediately, to place items in a plastic bag until they are washed. They should then seek medical advice from their GP or from their local hospital if any symptoms persist."