WORKING FOR A HEALTHY FUTURE

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Why does exposure generally decrease over time?

John W Cherrie, Karen Galea, Hilary Cowie, Joanne Crawford, Martie van Tongeren

Other collaborators: DT While, H Kromhout, A Agostini, F de Vocht, A Bolton, M Graham, AJ Soutar, J Tickner

Summary…

• Inhalation exposure to hazardous substances generally decreases over time

• What environmental or other factors cause these reductions?

• The Theory of Planned Behaviour (TPB) and exposure control

• Discussion of why exposures decrease • Flour dust• Wood dust, toluene and respirable dust in quarries• VCM

Methods…

• HSE National Exposure DataBase (NEDB) data:• toluene, flour dust, wood dust

• Collaborators data sets:• quarry data (respirable dust and quartz)• rubber manufacturing dust and fume data - ExAsRub database

• Follow-up sampling surveys:• previous wood dust, toluene and quarry dust sampling• similar measurement methods used• staff interviewed to try to identify reasons for changes in exposure

• Statistical analysis• concentration transformed onto the natural log scale• Mixed Effects Models

Exposures generally decrease…

Aerosols

Creely KS et al. (2007) Trends in inhalation exposure--a review of the data in the published scientific literature. Ann Occup Hyg.; 51(8): 665-678.

% change per year = 100 * (exp[β1] –1)

Exposures generally decrease…

Gases and vapours

Simulated exposure reduction at a plant

Five plants…

Ten plants…

25 plants…

Flour dust…

van Tongeren M et al. (2009) Trends of flour dust exposure in the United Kingdom, 1985–2003 Environ. Monit., 2009, 11, 1492 – 1497.

VCM levels in a English PVC plant

What changes?

• High pressure water jet cleaning• Removal of VCM residues by

stripping• Improved general ventilation• Use of scale inhibitors• Extraction on open reactor

vessels• Reduce leaks• Monitor the workplace air• Breathing Apparatus

The Theory of Planned Behaviour

Behavioural beliefs

Attitude towards the behaviour

Normative beliefs

Subjective norms

Control beliefs

Perceived behavioural

control

Intention Behaviour

Actual behavioural

control

http://people.umass.edu/aizen/tpb.diag.html

TPB…

Behavioural beliefsIf I improve the process I will increase profitabilityImproving the process will reduce exposure to chemical XImproving the process will improve working conditions

Attitude evaluations

Increasing profitability is…

• Target group: people who control a process• Behaviour: Improving a production process

Unlikely Likely

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

Extremely Extremely

undesirable desirable

-3 -2 -1 0 +1 +2 +3

TPB…

BI = Behavioral intention

AB = Attitude Toward Behavior

b = the strength of each belief

e = the evaluation of the outcome or attribute

SN : Social Normn = the strength of each normative belief

m = the motivation to comply with the referent

PBC = Perceived Behavioral Control

c = the strength of each control belief

p = the perceived power of the control factor

k = empirically derived weights

€

BI = k1AB(b + e) + k2SN(n + m) + k3PBC(c + p)

Investigation of changes in exposure…

Things changed…

What were the determinants of change?

• Economic• Market downturn – reduced production, less people• Improved efficiency – buying in ready-made

components

• Legislation• Environmental – achieve emissions targets• Health and safety – inspection visits, prosecution

• Safety culture• New owners – larger company• New managers – new ideas

What were the determinants of change?

Discussion…

• No change in flour dust exposure• Perceived as non-hazardous, little pressure from the

regulator to reduce exposure, traditional industry

• Wood dust, toluene and quarry dust decrease by about 3 to 8% per annum• “business as usual” changes driven by the regulators,

good information available about control measures

• VCM decreased by about 90% per annum• high concern about cancer risk, pressure for action from

regulators, lots of options to reduce exposure

Publications from the project…

• Creely KS, Cowie H, Cherrie JW et al (2007) Trends in inhalation exposure – a review of the data in the published scientific literature. Annals of Occupational Hygiene; 51: 665-678.

• Galea KS, van Tongeren M, Sleeuwenhoek AJ, et al. (2009) Trends in wood dust inhalation exposure in the UK, 1985-2005. Annals of Occupational Hygiene; 10.1093/annhyg/mep044.

• van Tongeren, Galea KS, Tickner J, et al (2009) Temporal trends in flour dust exposure in the United Kingdom, 1985-2003. Journal of Environmental Monitoring; 11: 1492 – 1497.

• Agostini M, de Vocht F, van Tongeren M, et al. Exposure to rubber process dust and fume since 1970s in the United Kingdom. The influence of origin of the measurement data. Plan to submit to Journal of Environmental Monitoring

• Sleeuwenhoek AJ, Galea, KS, van Tongeren M et al. Trends in respirable dust and quartz exposure in UK quarries. Plan to submit to Journal of Environmental Monitoring

• Possible overarching paper.