n-hexane

There was an interesting article in the Guardian a few days ago about the use of n-hexane in a factory in China. The company in question, which produces touch screens fro companies including Nokia, was using the solvent to clean the screens.

N-hexane is one of the organic compounds we study on BOHS Module course M101 ”Effects of hazardous substances”. As an alkane, we wouldn’t expect it to be particularly toxic. Alkanes generally are mild irritants and narcotics (substances that cause depression of the nervous system leading to effects similar to drunkenness). N-hexane is different in that it has been found to have another more serious chronic (i.e. long term) effect. Exposure to the compound can lead to peripheral neuritis – damage to the peripheral nervous system – causing symptoms such as loss of sensation in the fingers. There’s a good summary on the effects of n-hexane here.

The effects on the peripheral nervous systems are not due to the substance itself, but one of it’s metabolites - hexane-2,5-dione. It’s an example where the bitransformation of a substance in the body produces a more toxic compound.
The harmful effects are well known, and in the UK, Europe and the USA companies with a commitment to the health and safety of their workers would avoid using n-hexane wherever possible. It seems that the Chinese company actually used n-hexane as a substitute for the less toxic ethanol. According to the Guardian report about 49 workers were affected. The problem could have been avoided if a serious attitude was taken to health and safety and the principles of occupational hygiene were applied.

Selecting chemical protective gloves

Where gloves need to be worn for chemical protections its important that they are suitable for the chemical and application concerned and will provide protection for an appropriate time period. Too often inappropriate gloves are worn and even if suitable ones are used, they tend to be used long after they are capable of providing protection.

If it is necessary to use gloves then the first consideration is “what is the chemical we’re protecting against“. Once we know this data should be obtained from glove manufacturers on the breakthrough time, and the permeation rate. The breakthrough time is the time it takes for the chemical to work its way through the glove, which is normally well before any physical degradation has occurred. This will allow the most suitable glove to be selected, as breakthrough times for different gloves for a particular chemical will vary considerably. It will also usually allow the useful life of the glove to be defined – and the replacement frequency.

Degradation data should also be obtained – this is about the physical deterioration of the glove – as this can sometimes occur before breakthrough. Usability considerations are important too. It’s no good specifying gloves that aren’t usable because they’re not compatible with the work or the user.

Each manufacturer should provide data for their own products .

A pdf version of Ansell’s latest chemical resistance guide is available from here. They also have their information on line.

One of the other main suppliers, Marigold, also have an online guide.

Other manufacturer’s should have similar information available. If not, you can’t use their gloves for chemical protection.

New asbestos guidance

The HSE has jst launched it's new asbestos survey guide.

It can be ordered, or, even better, download for free from http://tiny.cc/6XNcH

"This heavily illustrated publication replaces and expands on MDHS100, surveying, sampling and assessment of asbestos-containing materials. It is aimed at people carrying out asbestos surveys and people with specific responsibilities for managing asbestos in non-domestic premises under the Control of Asbestos Regulations 2006. The book covers competence and quality assurance and surveys, including: survey planning, carrying out surveys, the survey report and the dutyholder's use of the survey information. It includes extensive appendices and references and it complements and supports other guidance on managing asbestos."

Girls Aloud on occupational health?

I wouldn't admit to being a fan of Girls Aloud - I'm not sure what it would do to my reputation of I did! However, it was good to see the article in the Observer today about the campaign by Nicola Roberts, the red headed, pales skinned member of the group, against the use of sunbeds by under 18s. She features in a documentary - "Nicola Roberts – The Truth About Tanning", on BBC3 on Thursday 4th February.

Excessive exposure to UV radiation can lead to a number of skin problems including malignant melanoma. Young people are particularly vulnerable. According to the International Agency for Research on Cancer, the risk of melanoma was increased by 75% in people who started using sunbeds regularly before the age of 30. Yet peer pressure forces many pales skinned young people to use sun beds to try to give themselves a fashionable tan.

We cover the risks of non-ionising radiation on BOHS module M201 "Thermal Environment and Non-ionising radiation" which we are running w/c 22 March. I can't promise that Girls Aloud will be performing though!

Photo credit: Flickr http://www.flickr.com/photos/22948324@N08/2520077527/

P601 and competence in LEV testing

I received the following query a few days ago:

A large part of my working life during the last 14 years has been involved with the Thorough Examination and Test of Local Exhaust Ventilation (LEV) systems within the company I work for.

I have now moved on within the same company to a health and safety position, but over the last two years, I have been training another person to carry out the LEV testing under my direct supervision. This person I feel is now capable of carrying out the full inspection and tests on his own.

Being qualified myself to the BOHS P601 standard, can I signs off the reports done by my trainee as being correct (if I feel they are done to a satisfactory standard) or does he need to prove he is competent himself by attending a formal course such as the P601.

This was my answer:

"COSHH requires that anyone carrying out any work required by the Regulations must be competent. This applies to the testing of LEV systems.

Passing P601 is a way of demonstrating competence to test LEV systems to an employer, client or the regulatory authorities. HSE strongly encourage those testing LEV systems to have passed P601, but it is not a legal requirement as such (although I do know of one situation where an Inspector placed an Improvement Notice on a company that required their personnel to take P601).

If you are certain that your colleague is competent and you could demonstrate this by some means if challenged (particularly by the HSE) then, it is probably not necessary for him to have taken the course. It is more important for consultancy/testing companies who provide a service to ensure there staff have the qualification as a means of reassuring the client that they know what they are doing. There are lots of companies offering LEV testing and not all of them are competent.

So, you need to make your own decision based on how confident you are that you can satisfy the HSE that your colleague is competent.

Of course, the above is only my personal opinion. A HSE Inspector could have a different view!"

What's a safe dose?

It was interesting to see an article in The Guardian yesterday discussing dose response relationships and threshold doses. Generally, increasing the dose of a substance increases the severity of the effect it causes. Similarly, for a given effect, due to individual susceptibility increasing the dose leads to an increase in the response – i.e. the number of people affected. For most substances, however, there is a threshold dose – that is a dose below which no-one is affected. This is because at doses below he threshold, the body’s mechanisms can deal with the substance, preventing harm. This can be represented graphically.

Typical dose-response curve showing a "threshold dose" (source:http://www.unido.org/index.php?id=5297)

With some substances, such as carcinogens and sensitisers, it is not possible to detect a threshold experimentally. It is argued that this is because they do not have one . The response is still dependant on the dose and at very low doses there are still some people who will be affected, albeit a relatively small number. Nevertheless, there is no “safe dose”. In such cases the dose-response curve is likely to be linear.

The Guardian article discusses the views put forward by an Oxford University physicist, Wade Allison, who has published a book in which he argues that there is a threshold for the effects of ionising radiation. He contends that DNA damage caused by exposure below this threshold dose can be repaired by the cells natural processes. This goes against the established view that radiation, like other direct acting carcinogens, has a dose response curve which doesn’t have a threshold, so that there is no identifiable dose below which adverse effects do not occur. Other radiation specialists are quoted in the article who do not support his view.

The difficulty with carcinogens is that at low doses it isn’t possible to accurately determine whether there is an effect. Cancer can be caused by many agents, including some related to lifestyle (e.g. smoking) and natural sources (e.g. background radiation from cosmic radiation and from rocks) and in reality we are normally simultaneously exposed to multiple agents. At low doses a carcinogen, such as radiation, is only associated with very low incidences of the disease. So it can be difficult to determine exactly what is the causative agent. If there is a threshold, it is likely to be very low, and detecting it would be difficult.

HSE Publications on-line

When I was a young junior occupational hygienist working in industry (a long, long time ago!) one of my bosses' favourite sayings that an occupational hygienist is only as good as his information sources, and, consequently, he always emphasied the importance of having a good library of books and other documents. Of course, in those days, before the advent of the Internet, we had to rely on text books and printed copies of documents published by HSE, NIOSH, ACGIH. It was important that they were kept up to date which entailed purchasing new copies of documents we already had when a new edition came out.

The Internet has changed this to a large extent. Many information sources are now online. This has the benefit of easy acess and ensures that you have the most up to date information - printed documents (particularly toxicological information) can be out of date the moment its published!

The HSE have been quite slow in putting information on-line. The HSE website has improved over the years but the information available has been restricted. Many of their key publications had to be purchased via HSEbooks. They were clearly seen as a source of income. However, this has changes as fairly recently the hSE has made many of their key publications available on-line as pdf documents. They can be read on-line or downloaded from here.

Particularly useful documents now available free of charge include

• HSG173: Monitoring strategies for hazardous substances
• HSG258 : Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV)
• HSG53 : Respiratory protective equipment at work: A practical guide
• The COSHH ACoP
  
• HSG 170 : Vibration solutions: Practical ways to reduce the risk of hand-arm vibration injury
• L108 : Controlling Noise at Work