August 29, 2017

expert reaction to chemical haze in sussex

Experts react to the news of a chemical haze at Beachy Head in Sussex.

Alastair Hay, Professor (Emeritus) of Environmental Toxicology, University of Leeds said:

“It’s hard to say much about this at the moment.

“The advice is sensible. Stay indoors. Wash eyes with fresh water. If the cloud moves staying indoors will provide some protection. After some time however, air inside is the same as that outside so will no longer be as protective. Hope for wind to disperse cloud.

“Priority is to identify cloud. Detectors are available and Draeger tubes can be used. Also find source.  But, source may already know and stopped release, but cloud may continue for some time if slow moving. The fact that it is relatively close to the ground suggests a heavier than air compound,   and an irritant like chlorine (which is twice the weight of air)  would travel in this  way.

“People’s response suggests the cloud contains irritants hence stinging eyes and sore throats. Keep out of cloud as advised by emergency services and suck lozenges etc. for sore throat.”

David Slater, Hon Prof, School of Engineering, Cardiff University, said

“For what it’s worth, it seems a pretty localised phenomenon and I’d look for a local source.

“On Google there seems to be a discharge into the sea at that point and just inland is a water treatment works.

“Looks like Southern water from the sign and its apologising for some inconvenience.

“From my experience in regulating water companies, unplanned discharges are not uncommon!

“They report (BBC) that – Those caught in the mist say it felt like “being in a swimming pool with large quantities of chlorine”.

My guess would be accidental discharge of treatment chemicals (say over chlorinated waste water) into a warm sea.”

Dr Michael Walker, LGC,  provided the following information:

Chlorine

There are conflicting reports as to the likelihood of the mist being associated with chlorine; one report in the media cites a witness as comparing the smell to that of chlorine (swimming pool water), while the East Sussex Fire and Rescue Service said it was “extremely unlikely” the substance involved was chlorine (http://www.bbc.co.uk/news/uk-england-sussex-41070002 )

If it was chlorine the following may be of interest.

Chlorine is a yellow-green gas at room temperature with a pungent, irritating odour similar to bleach that is detectable at low concentrations. The vapour density of Chlorine gas is approximately 2.5 times greater than air, which will cause it to initially remain near the ground in areas with little air movement.  It is slightly water soluble, and reacts with moisture to form hypochlorous acid (HOCl) and hydrochloric acid (HCl). The Health Protection Agency has summarised the toxicology of Chlorine as follows. Exposure of unprotected personnel to Chlorine gas may initially result in eye and lung irritation, the severity of which will be dependent on the concentration and duration of contact. Relatively minor exposures may result in sensory irritation such as burning of the eyes and throat. These initial symptoms are caused by free-radicals, hypochlorous acid formed by the reaction of chlorine with water in lung or eye tissues. More significant exposures may lead to coughing and breathing difficulties due to the development of pulmonary and/or laryngeal oedema. There is some evidence to suggest that acute exposure may result in long-term pulmonary sequelae (reactive airways dysfunction; RADs) in a small proportion of individuals although one report relating to accidental exposure to chlorine gas suggests that chronic sequelae following acute exposure may be more frequent than previously anticipated. Immediate symptoms following inhalation include a burning sensation in the eyes and pain or burning of the lungs during respiration. Sufficient exposure may induce reflex cholinergic bronchoconstriction with associated signs of coughing, wheezing and dyspnoea. Exposure to a sufficiently high dose may result in pulmonary oedema and respiratory failure, the onset of which may be delayed by up to 36 hours. In extreme cases, pulmonary haemorrhage may also occur.

Table 1: Summary of acute toxic effects in relation to approximate air concentrations of chlorine 

It is likely, given the symptoms notes, that if chlorine was the principle gas involved concentrations were between 1 and 30 ppm.

Workplace Exposure Limits (WEL) for Chlorine are as follows:

Table 2:   Workplace Exposure Limits (WEL) for Chlorine

It is relatively difficult to convert occupational exposure standards from the workplace to a non-industrial situation but a factor of at least 1/10 should applied to a short time exposure in order to allow for those exposed who may be younger or older than the general workforce and for those in less good health than in the workforce. This would mean that short-term concentrations of the order of more than 0.29 mg m^-3 should be viewed as unacceptable.

The release of Chlorine could occur by a number of means:

• Reaction of swimming pool chemicals accidentally mixed is an accident that is relatively rare but well known
• Release of chlorine gas from water treatment facilities has occasionally occurred
• Venting of chlorine gas from chemical tankers at sea is another possibility

Dr. Simon Boxall, University of Southampton, National Oceanography Centre said:”I noted the story but as yet there is limited information coming out.  I wouldn’t jump at the assumption it has come across the Channel.  In terms of waterborne pollutants these can’t track from France to the area and looking at the weather data from Lydd Airport the winds have been very light (building to a max of 10mh this evening) but more critically from the east/North East and from the North earlier in the day. This means that it is highly likely that any effect will have come from the UK side or (possibly) a vessel running close to shore with the tide bringing the material towards the beach.  It could also have come from vessels in the Dover Strait.

“One slight update – looking at the weather station at Wimereux on the French side there was a slight offshore breeze this morning, up until about midday which could possibly have brought an air mass into the Dover Strait  which then moved westwards towards Eastbourne – so not impossible it came from the French Coast.”

“Further update.  If the reports from the public are to be relied on it is weird that the “cloud” rolled in from the West. This is against the very light winds which should have driven in from the east. This implies a water borne cause.  Having slept on it – the conditions yesterday were ideal for the development of a toxic algal bloom (very calm, high light levels, a period of moderate runoff inputting high levels of nutrients into the sea for the preceding weeks).  There are some published studies in the US (c. 2009/11) which show that in are cases the toxins from the harmful algal bloom can form aerosols which enter the atmosphere and drift adore.  These cause respiratory problems and irritation, particularly in those with Asthma.  A long shot but the evidence points in that direction….!!”

Non-attributable comment: “The only possibility I can think of is that it might be a container of chemicals washed off a ship and ruptured. It might not necessarily be chlorine as there are other chemicals which produce a similar smell and reaction when mixed with water.

E.g. Thionyl Chloride reacts with water to form Hydrochloric Acid and Sulphur Dioxide, which is an unpleasant combination (from experience!) Other chemicals such as Benzyl Chloride (a common constituent of plastics) react with water for form Hydrochloric Acid.

Acetic Anhydride reacts with water to form acetic acid which will also make eyes sting and give difficulty breathing.

Other common chemicals would include Chlorsulphonic acid (forms sulphuric and hydrochloric acids in contact with water).

Until the exact nature of the chemical is established it is not possible to make any realistic predictions or accurate comments.

One more remote possibility would be old munitions, but there are no old munition dumps in the area that I am aware of.”