Politicians are expected to be among those queueing up in Cardiff to have their blood tested for dangerous chemicals.
Campaigners say dangerous chemicals are found in blood
Environmental campaigners operating from a mobile testing unit near the Welsh Assembly headquarters in Cardiff Bay will be hoping to highlight their plea for many man-made chemicals to be phased out.
Environmental campaigning group WWF hope Assembly Members will spare a few minutes to have the test done.
The organisation is concerned that even low doses of certain chemicals may be dangerous.
The test centre is in Wales as part of a tour throughout Britain.
Scientists will examine blood for more than 70 artificial chemicals found in pesticides, cosmetics and plastics which could be in the volunteers' bodies.
The tour is sponsored by WWF, the Womens' Institute and the Co-Op bank, all of whom want European Union legislation to phase out the chemicals.
The chemical industry denies, however, that there are any health dangers.
Campaigners claim that existing laws controlling controlling the manufacture and use of chemicals are inadequate.
New legislation covering legislation is due to be negotiated in the EU this year and next.
But the WWF says there is "no guarantee" that new legislation would offer enough protection from hazardous chemicals.
It wants Britain and other European countries to place restrictions on such chemicals and use safer alternatives.