Tuesday, September 17, 2013

Will your drinking water poison you?

The addition of fluoride to drinking water has remained controversial so we are greatly indebted to the massive and very thorough literature review below  -- which summarizes the available evidence on the question.  And what it finds is that there is no cause for alarm. 

Scientific studies very rarely find exactly zero differences between two groups.  Zero effect is however recognized if the difference is very small.  SOME differences will arise due to random variations alone.  And the  results below show a tiny difference and hence signify zero real difference between the groups, meaning that no concern about fluoride is warranted.

An important source of random variation in the study is that IQ testing is just not fine-grained enough to recognize true differences of less than one point. And it was a difference of less than half of one point that was found in the work below. Large differences in IQ score are highly diagnostic of many things but tiny differences are simply unreliable as predictors. The authors are clearly not familiar with the psychometrics of IQ research.  IQ tests are not a magic black box.  They have to be used and interpreted with care.

I note that statistical significance was achieved for the results reported.  Statistical significance is only a first condition for work to be taken seriously, however.  It shows that the results are not due to just one source of random variation: small sample size.  Since the sample below was large, that finding is essentially irrelevant

The authors below seem to think that they have found something alarming.  After all the work they did, I suppose they would.  They have lost perspective.  These are resoundingly negative results

The journal abstract:

Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis

Anna L. Choi


Background: Although fluoride may cause neurotoxicity in animal models and acute fluoride poisoning causes neurotoxicity in adults, very little is known of its effects on children’s neurodevelopment.

Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development.

Methods: We searched the MEDLINE, EMBASE, Water Resources Abstracts, and TOXNET databases through 2011 for eligible studies. We also searched the China National Knowledge Infrastructure (CNKI) database, because many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups. Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking-water fluoride as the only exposure. We performed the Cochran test for heterogeneity between studies, Begg’s funnel plot, and Egger test to assess publication bias, and conducted meta-regressions to explore sources of variation in mean differences among the studies.

Results: The standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease.

Conclusions: The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.


Could the winter vomiting bug be wiped out by brass taps and fittings? Study finds the virus can't survive on copper

Very interesting indeed

The winter vomiting bug could be virtually wiped out by reintroducing brass taps and fittings, according to new research.

A study has found norovirus cannot survive on the metal, offering hope of a cheap and effective way of reducing the 267 million cases of acute gastroenteritis it causes each year.

The highly infectious bug costs the National Health Service at least £100 million annually, with up to 3,000 people admitted to hospital each year.

There is no treatment or vaccine, and outbreaks require expensive cleaning, with lost working days when staff are infected adding to the burden.

Its impact is also felt beyond healthcare, with cruise ships and hotels suffering significant damage to their reputation when epidemics occur among guests.

Dr Sarah Warnes, of the University of Southampton, said: ‘The use of antimicrobial surfaces containing copper in clinical and community environments, such as cruise ships and care facilities, could help to reduce the spread of this highly infectious and costly pathogen.’

The virus can be contracted from contaminated food or water, person to person contact and contact with contaminated surfaces, meaning those made from copper could effectively shut down one avenue of infection.

A study designed to simulate fingertip touch of surfaces showed norovirus in room temperature was rapidly destroyed on copper and its alloys, with those containing more than 60 per cent proving particularly effective.

The rate of destruction was initially very rapid and proportional to the copper content. No such effect was found on stainless steel.

Copper alloys have previously been shown to be effective antimicrobial surfaces against a range of bacteria and fungi.

Dr Warnes said: ‘Copper alloys, although they provide a constant killing surface, should always be used in conjunction with regular and efficient cleaning and decontamination regimes using non-chelating reagents that could inhibit the copper ion activity.’

Professor Bill Keevil added: ‘Although the virus was identified over 40 years ago, the lack of methods to assess infectivity has hampered the study of the human pathogen.

‘The virus can remain infectious on solid surfaces and is also resistant to many cleaning solutions.  ‘That means it can spread to people who touch these surfaces, causing further infections and maintaining the cycle of infection.

‘Copper surfaces, like door handles and taps, can disrupt the cycle and lower the risk of outbreaks. What we have found is the metal destroys the genetic material of the norovirus.

‘In the U.S., 100,000 people die each year from hospital acquired infections. In the UK, I believe the figure is about 5,000. If a healthy person gets norovirus they are sick for a couple of days, and then get over it. But for an elderly person, it can be fatal. The figures are frightening.

‘If you build a hospital, a care home or a liner from scratch using copper instead of stainless steel, the cost will be about the same.

‘Brass fittings were used in hospitals forty or fifty years ago, since when we have gone over to stainless steel. During this time hospital acquired infections have soared. Is that a coincidence?’

Earlier research has found copper fittings rapidly kill bugs on hospital wards, succeeding where other infection control measures fail.

In a ten week study at Selly Oak Hospital, Birmingham, copper taps, toilet seats and push plates on doors all but eliminated common bugs.

It is believed the metal 'suffocates' germs, preventing them breathing. It may also stop them from feeding and destroy their DNA.

Lab tests show that the metal kills off the deadly MRSA and C difficile superbugs. It also kills other dangerous germs, including the flu virus and the E coli food poisoning bug.

Although it is usually thought to be an expensive metal, copper is actually a similar price to stainless steel.


1 comment:

Wireless.Phil said...

Well: The Arsenic in Our Drinking Water
The baby with the runny nose, the infant with a stubborn cough — respiratory infections in small children are a familiar family travail. Now scientists suspect that these ailments — and many others far more severe — may be linked in part to a toxic element common in drinking water.