parallel to low radiologic dose effect

[M Nivas <motnivas@YAHOO.COM>]

This may be of interest.  It is parallel to low

radiologic dose effect.



  Dangerous levels of toxins miscalculated

Potential pollutants and poisons may be beneficial in

low doses. 

13 February 2003 

HELEN R PILCHER 



 

We may be putting too much effort into cleaning our

enviroments. 

© Corbis 

 

The levels at which potentially toxic substances such

as mercury and lead are classified as dangerous may

have been miscalculated, two US scientists are

warning. Risk assessments and regulations on safe

limits for these substances in medicine and the

environment may have to be rethought, they warn1.



There are safe levels below which potential pollutants

and poisons may actually be beneficial, say Edward

Calabrese and Linda Baldwin of the University of

Massachusetts in Amherst. For the past 30 years,

cancer-causing chemicals and X-rays have been viewed

largely as dangerous whatever their level. 



"The field of toxicology has made a terrible blunder,"

says Calabrese. "A lot of high-powered people need to

take the time to explore this."



For example, dioxins, which are industrial by-products

that at certain doses can cause cancer, can actually

reduce tumour growth in some species. Similarly, small

amounts of the toxic trace metal cadmium can promote

plant growth. 



"What we call 'toxic chemicals' is a misnomer," says

cell biologist and UK government advisor Anthony

Trewavas from Edinburgh University. "Mild chemical

stress is beneficial." 



Having identified over 5,000 similar examples,

Calabrese and Baldwin are among a growing number of

researchers who feel that the hazardous nature of

toxic substances has been overstated. The levels used

in studies are not comparable to those normally

experienced by humans, Calabrese says. "This provides

an interesting challenge for the clinical and

pharmaceutical industries as they develop new

medicines."



The point of toxicological testing is to determine the

drug exposure at which undesired effects are observed 

UK Medicines Control Agency 

 

 



Britain's Medicines Control Agency (MCA) is more

cautious. "The point of toxicological testing is to

determine the drug exposure at which undesired effects

are observed," a spokesperson said, adding that the

new criticisms are, "unlikely to change the way in

which the MCA or other regulatory agencies conduct

product risk-benefit analysis."



The debate also raises the question of how clean our

environment really needs to be. Some argue that

billions of dollars are being wasted ridding the world

of substances that are dubbed 'hazardous', when low

levels could actually be a good thing. 



"We don't need to spend large amounts of money on

removing chemicals from the environment," says

Trewavas. "Food contains lots of natural chemicals

that are as damaging as synthetics. We consume lots of

these all the time without harm. The public need

re-educating in this."



But convincing people that 'safest' is a more

meaningful description of risk than 'safe' and

'dangerous' is notoriously difficult. 

 

 

References

Calabrese, E.J. & Baldwin, L.A. Toxicology rethinks

its central belief. Nature, 421, 691 - 321, (2003).

|Article| 

 

 

 





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