OccupationalHygieneEDITED BY

Kerry GardinerBSc, PhD, Dip. Occup. Hyg., FFOH

Professor of Occupational Health

The Medical School

The University of the Witwatersrand

Johannesburg

South Africa

and

International Occupational Health Ltd

Edgbaston

Birmingham, UK

J. Malcolm HarringtonCBE, BSc, MSc, MD, FRCP, FFOMI, MFPH, FMedSci

Emeritus Professor of Occupational Medicine

The University of Birmingham

Edgbaston

Birmingham, UK

THIRD EDITION

Occupational Hygiene

OccupationalHygieneEDITED BY

Kerry GardinerBSc, PhD, Dip. Occup. Hyg., FFOH

Professor of Occupational Health

The Medical School

The University of the Witwatersrand

Johannesburg

South Africa

and

International Occupational Health Ltd

Edgbaston

Birmingham, UK

J. Malcolm HarringtonCBE, BSc, MSc, MD, FRCP, FFOMI, MFPH, FMedSci

Emeritus Professor of Occupational Medicine

The University of Birmingham

Edgbaston

Birmingham, UK

THIRD EDITION

� 2005 by Blackwell Publishing Ltd

Blackwell Publishing, Inc., 350 Main Street, Malden, Massachusetts

02148-5020, USA

Blackwell Publishing Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK

Blackwell Publishing Asia Pty Ltd, 550 Swanston Street, Carlton,

Victoria 3053, Australia

The right of the Authors to be identified as the Authors of this Work has been

asserted in accordance with the Copyright, Designs and Patents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in

a retrieval system, or transmitted, in any form or by any means, electronic,

mechanical, photocopying, recording or otherwise, except as permitted by

the UK Copyright, Designs and Patents Act 1988, without the prior

permission of the publisher.

First published 1980

Second edition 1995

Reprinted 2002

Third edition 2005

Library of Congress Cataloging-in-Publication Data

Occupational hygiene / edited by K. Gardiner, J.M. Harrington.– 3rd ed.

p. ; cm.

Includes bibliographical references and index.

ISBN-10: 1-4051-0621-2

ISBN-13: 978-1-4051-0621-4

1. Industrial hygiene. 2. Industrial toxicology.

[DNLM: 1. Occupational Health. 2. Accidents, Occupational–prevention & control.

3. Occupational Diseases–prevention & control. WA 440 01497 2005] I. Gardiner,

K. II. Harrington, J. M. (John Malcolm)

RC963.0224 2005

613.6’2–dc222004025327

A catalogue record for this title is available from the British Library

Set in 9.5/12 pts Sabon by Kolam Information Services Pvt. Ltd, Pondicherry, India

Printed by Gopsons Papers, Noida, India

Commissioning Editor: Alison Brown

Editorial Assistant: Claire Bonnett

Production Editor: Fiona Pattison

Production Controller: Kate Charman

For further information on Blackwell Publishing, visit our website:

http://www.blackwellpublishing.com

The publisher’s policy is to use permanent paper from mills that operate a sustainable

forestry policy, and which has been manufactured from pulp processed using acid-free

and elementary chlorine-free practices. Furthermore, the publisher ensures that the text

paper and cover board used have met acceptable environmental accreditation standards.

Contents

List of contributors, vii

Preface, ix

Part 1: Introduction

1 Occupational hygiene 3

Kerry Gardiner

2 Global strategies and trends in occupational

health: well-being at work in focus 6

Bengt Knave

Part 2: Organ structure and function

and the adverse effects of work

3 The structure and function of the lungs 13

J. Malcolm Harrington and Anthony

J. Newman-Taylor

4 Organ structure and function: the skin 25

Iain S. Foulds

5 Musculoskeletal disorders 36

Grahame Brown

6 The effects of inhaled materials on the lung

and other target organs 47

Jon G. Ayres

7 The effects of some physical agents 59

Philip Raffaelli

8 Toxicology 67

Julian Delic, Steven Fairhurst

and Maureen Meldrum

Part 3: Principles of occupational hygiene

9 The nature and properties of workplace

airborne contaminants 85

Lisa M. Brosseau and Claudiu T. Lungu

10 Principles of risk assessment 105

Steven S. Sadhra

11 Design of exposure measurement surveys

and their statistical analyses 124

Hans Kromhout, Martie van Tongeren

and Igor Burstyn

12 Retrospective exposure assessment 145

Tom J. Smith, Patricia A. Stewart

and Robert F. Herrick

13 Biological monitoring 160

Tar-Ching Aw

14 Epidemiology 170

J. Malcolm Harrington

Part 4: Environmental hazards:

principles and methods of their

assessment

15 The sampling of aerosols: principles and

methods 185

David Mark

16 The sampling of gases and vapours:

principles and methods 208

Richard H. Brown

17 Noise 222

Kerry Gardiner

18 Vibration 250

Michael J. Griffin

19 Light and lighting 268

N. Alan Smith

20 The thermal environment 286

Antony Youle

21 Non-ionizing radiation: electromagnetic

fields and optical radiation 307

Philip Chadwick

v

22 Ionizing radiation: physics, measurement,

biological effects and control 328

Ronald F. Clayton

23 Biological agents 344

Julia M. Greig and Chris J. Ellis

24 Psychological issues 360

Anne Spurgeon

25 The development of ergonomics as a

scientific discipline 373

Joanne Crawford

26 Dermal exposure assessment 389

John W. Cherrie

Part 5: Allied and emerging issues

27 Occupational accident prevention 403

Richard T. Booth and Anthony J. Boyle

Part 6: Control

28 Work organization and work-related

stress 421

Tom Cox, Amanda Griffiths and

Stavroula Leka

29 Control philosophy 433

Kerry Gardiner

30 Ventilation 440

Frank Gill

31 Personal protective equipment 460

Robin M. Howie

32 Occupational health and hygiene

management 473

Lawrence Waterman and Karen Baxter

Contents

vi

Contributors

Tar-Ching AwDivision of Occupational Health

Kent Institute of Medicine and

Health Sciences

University of Kent

Canterbury, UK

Jon G. AyresDepartment of Environmental

and Occupational Medicine

University of Aberdeen

Aberdeen, UK

Karen BaxterSypol Limited

Aylesbury, UK

Richard T. BoothHealth and Safety Unit

School of Engineering

Applied Science

Aston University

Birmingham, UK

Anthony J. BoylePriors Marston

Warwickshire

Lisa M. BrosseauUniversity of Minnesota – School of

Public Health

Division of Environmental

Health Sciences

Minneapolis, MN

USA

Grahame BrownRoyal Orthopaedic Hospital NHS Trust

Northfield

Birmingham, UK

Richard BrownResearch & Laboratory

Services Division

HSE

Sheffield, UK

Igor BurstynDepartment of Public Health Sciences

University of Alberta

Edmonton

Canada

Philip ChadwickMicrowave Consultants Limited

Newbury

Berkshire, UK

John W. CherrieInstitute of Occupational Medicine

Riccarton

Edinburgh, UK

Ronald F. ClaytonAbingdon, UK

Tom CoxInstitute of Work, Health and Organisation

University of Nottingham

Nottingham, UK

Joanne CrawfordUniversity of Birmingham

Institute of Occupational and

Environmental Medicine

Edgbaston

Birmingham, UK

Julian DelicHSE

Magdalen House

Bootle, UK

Chris J. EllisDepartment of Infection

Heartlands Hospital

Bordesley Green

Birmingham, UK

Steven FairhurstHSE

Bootle, UK

Iain S. FouldsBirmingham City Hospital

Birmingham Skin Centre

Birmingham, UK

Kerry GardinerThe Medical School

The University of Witwatersrand

Johannesburg

South Africa

and

International Occupational Health Ltd

Edgbaston

Birmingham, UK

Frank GillSouthsea

Portsmouth, UK

Julia M. GreigDepartment of Infection

Heartlands Hospital

Bordesley Green

Birmingham, UK

Michael J. GriffinHuman Factors Research Unit

Institute of Sound and Vibration

Research

University of Southampton

Southampton, UK

Amanda GriffithsInstitute of Work, Health and

Organisation

University of Nottingham

Nottingham, UK

J. Malcolm HarringtonEmeritus Professor of Occupational

Medicine

The University of Birmingham

Edgbaston

Birmingham, UK

Robert F. HerrickDepartment of Environmental

Health

Harvard School of Public Health

Boston, MA

USA

Robin M. HowieRobin Howie Associates

Edinburgh, UK

vii

Bengt KnaveNational Institute for Working Life

Stockholm

Sweden

Hans KromhoutInstitute for Risk Assessment Sciences

Utrecht

Netherlands

Stavroula LekaHealth Psychology

Institute of Work, Health and

Organisation

University of Nottingham

Nottingham, UK

Claudiu T. LunguUniversity of Minnesota – School of

Public Health

Division of Environmental

Health Sciences

Minnesota, MN

USA

David MarkHealth and Safety Laboratory

Exposure Co.

Sheffield, UK

Maureen MeldrumHSE

Bootle, UK

Anthony J. Newman-TaylorRoyal Brompton Hospital

National Heart and Lung Institute

Imperial College School of Medicine

London, UK

Philip RaffaelliChief Executive

Headquarters Defence Medical

Education and Training Agency

Gosport, UK

Steven S. SadhraInstitute of Occupational and

Environmental Medicine

University of Birmingham

Edgbaston

Birmingham, UK

Tom J. SmithEnvironmental Health

Harvard School of Public Health

Boston, MA

USA

N. Alan SmithInstitute of Occupational and

Environmental Medicine

The Medical School

University of Birmingham

Birmingham, UK

Anne SpurgeonUniversity of Birmingham

Institute of Occupational and

Environmental Medicine

Edgbaston

Birmingham, UK

Patricia A. StewartOccupational Studies Section

National Cancer Institute

Rockville, MD

USA

Martie van TongerenCentre for Occupational and

Environmental Health

University of Manchester

Manchester, UK

Lawrence WatermanSypol Limited

Aylesbury, UK

Antony YouleRobens Centre for Occupational

Health and Safety, EIHMS

University of Surrey

Guildford, UK

Contributors

viii

Preface

A quarter of a century has passed since TonyWaldron first suggested to one of us (JMH) that there was no

available text for occupational hygienists. With much temerity and some trepidation, two physicians

attempted to fill that gap – with some apparent success. A second edition added an occupational hygienist

(KG) as editor. That edition sought to broaden the subjects covered as the discipline of occupational

hygiene became more clearly defined and the need for skills in recognising, evaluating and controlling

work environments became more pressing.

Major developments in the way in which occupational hygiene is taught and practised have followed in

the past decade. This period of time has also witnessed dramatic changes in the world of work and, with it,

the nature and type of health problems encountered at work. Whilst many of the classic occupational

diseases unfortunately still exist in the world’s poorer economies, in the developed world the main

challenges now are musculoskeletal disorders and psychosocial problems. These appear to be consequent

upon the rapid and continuing changes taking place in work organization.

At the same time, the boundaries between occupational medicine and occupational hygiene have

become blurred as increasing emphasis has been placed on team solutions to the ever more complex

work environment. We have attempted to include these newer issues in this edition and we hope that the

work/health problems we, as professionals, attempt to control are appropriately and adequately covered

in this revised and expanded text.

Kerry Gardiner, Birmingham

Malcolm Harrington, London

January 2005

ix

Part 1

Introduction

Chapter 1

Occupational hygiene

Kerry Gardiner

Background

The essential tenets of occupational hygiene as a

discipline (i.e. separating people from unpleasant/

deleterious situations/exposures) have been known

for centuries, but, as a profession, occupational

hygiene is in its relative infancy. There is much

debate about the first recognition of the profes-

sion, whether it was first described in Agricola’s

treatise in the mid-sixteenth century or resulted

from the fractious discourse between the Bureau

of Labor Standards (which wanted to create good

working conditions) and the US Public Health Ser-

vice (which focused on the post hoc recognition of

disease by means of clinical examination) (Carter,

2004). This difference in emphasis (a priori pre-

vention/control versus post hoc diagnosis) has

been pivotal in the progression (or otherwise) of

occupational health/hygiene over the years.

Albeit in simplistic terms, definitions of occupa-

tional hygiene (all of which contain most, if not all,

of the following: anticipation, recognition, evalu-

ation and control) are little different in overall

philosophy from any other part of occupational

health. However, as alluded to above, what has

changed in more recent years is a paradigm shift

away from the belief that it is best practice to

diagnose disease and try and identify a cause

(often against a background of limited opportunity

for treatment), towards a culture of risk mitiga-

tion/moderation by utilization of assessments of

the working environment in advance of any harm

being caused (Fig. 1.1).

Challenges

One area in which there is consensus amongst the

relevant professions is that of the breadth of dis-

ciplines and/or skills required to address ad-

equately modern working environments and the

people who work within them. This is evident in

terms of both the recognition of the various aspects

that affect an individual’s well-being outwith work

(i.e. genetics, environment, housing, diet, pre-

existing morbidity) and the complexity of modern

working environments [i.e. electromagnetic fields,

working hours/shift work, psychosocial hazards

(physical verbal abuse at or during work), chem-

ical risks] (Fig. 1.2). The resultant benefit is that

there appears to be greater recognition that the

professions must share their knowledge/expertise,

that each of the disciplines can indeed address

areas that historically were demarcated to be

their sole preserve and that each, and all, have an

essential role to play in the prevention/reduction of

ill health at work.

An additional challenge to all occupational

health professionals/disciplines (including occupa-

tional hygiene) is that there is a state of flux regard-

ing the nature of work and the social contracts

entered into by each individual/group. There is a

marked move away from the historic manufactur-

ing industries in the developed world towards very

specialized/technical work employing few but gen-

erating many risks along with the proliferation of

the ‘service industry’ and all that it encompasses.

This goes some way to explaining the dynamic

Background

Challenges

Political/financial context

The future, our contribution

Reference

3

shift of the hazard groups but implies so much

more. In many societies, despite the absence of

classic ‘chemical’ exposures, work still has a mas-

sive impact on people’s lives, from the individuals

who regularly work 80-hour weeks to the employ-

ees in call centres, who are frequently abused ver-

bally in the course of their work. The implied

corollary is that of ‘technology export’, wherein

processes deemed too hazardous, too restricted or

simply too expensive are moved to countries where

these factors are not or need not be a problem. The

irony is that it is very common for such large-scale

technology transportation to import standards of

living, general or occupational health care and

social infrastructure not otherwise available or

possible.

To complicate matters further, there is real con-

cern in the Western world of the impact of such

social phenomena as ageing workforces (differen-

tial impact of the hazards by age, protracted

periods of exposure, the psychological desire to

have retired at a reasonable age, etc.), peripatetic

workforces, in which the expectation of both the

employer and employee is that they will not remain

employed in any one company/place for very long

(thereby exacerbating the negative view of invest-

ing in training, the benefits of providing good oc-

cupational health care, the ability to undertake

Exposure Effect

Design

Pre-employment

Exposurereduction

Prevention/administrative

controls

Healthsurveillance

Relocate/rehabilitate

Relocate/rehabilitate

Figure 1.1 The importance of achiev-

ing control before the manifestation of

disease.

Workplace

Occupationalexposure

Pre-existenthealth status

Healthoutcome

Habits Death

Health

Clinicaldisease

Latentdisease

Psycho-social

Socio-economics

Genes

Diet

Environ-ment

Figure 1.2 The multifactoral nature of occupational health/hygiene.

Chapter 1

4

quality epidemiology, etc.), and migrant work-

forces (limited knowledge of previous occupa-

tional history).

It is exactly to address this ever-growing field

that this book has grown not only in size since its

first and second editions but also in the breadth of

the subject areas included. Clearly, the chapters

are not an exclusive list but are considered by

the editors to be the more pivotal aspects of the

discipline.

Political/financial context

In many ways, the effect of such ‘technical/profes-

sional’ issues is entirely dependent upon the polit-

ical and financial context within which

occupational health operates. Despite many gov-

ernments around the world utilizing persuasive

rhetoric to commit themselves to occupational

health – in the form of well-being at work, valuing

the country’s greatest asset, its people and so on –

this stance is often not put into practice.

Notwithstanding the fact that non-compliance

with occupational health statute is a breach of

criminal law in many countries, it is often of

great surprise to those not familiar with the discip-

line that it should be ‘policed’ in the way in which

it is, with the enforcing authorities usually hugely

underfunded and resourced, e.g. in the UK, at or

around the millennium, the Health and Safety Ex-

ecutive received �£200 million, whereas tax rev-

enues exceeded £3.2 billion and the police force

received £46 billion; no inference is made vis-a-vis

the relative importance but their difference is pro-

found. Despite the crudeness of these figures, they

ably demonstrate the stark contrast between how

society, through its elected representatives, views,

and ultimately values, the well-being of its work-

force and other sectors of the community. An

American colleague once recounted a wonderfully

apt phrase in relation to the way in which organ-

izations/agencies/government departments are

provided with sufficient funds to exist but expli-

citly not to be effective – ‘funded to fail’.

The future, our contribution

The text above is meant to provide the reader

solely with a context within which to read the

following chapters and, also, if the reader is a

student within the discipline or profession, some

guidance regarding the context within which he or

she will have to operate. It is not meant to be

negative in any way but to create a backdrop to

highlight quite how important ‘our’ field is; in fact,

in many ways, those that utilize the skills/know-

ledge of occupational hygiene (whether a profes-

sional, sister-discipline or interested layperson) are

as vital today as they were 100 years ago – it is just

that the rules have changed.

The greatest contribution that occupational hy-

gienists, and those that utilize their skill/know-

ledge base, can achieve is that they enable

potentially ‘risky’ processes to be undertaken in

relative safety. Society and individuals thrive on

risk and risk-taking, and those practising good

occupational hygiene principles facilitate this to

continue; after all, the biggest societal impact con-

cerning work is having no job at all. If we can

ensure that the workforce is ‘Healthy, Happy and

Here’ then we will have succeeded.

Reference

Carter, T. (2004). British occupational hygiene practice

1720–1920. Annals of Occupational Hygiene, 48,299–307.

Occupational hygiene

5

Chapter 2

Global strategies and trends in occupational health:well-being at work in focus

Bengt Knave

The changing work life

During the past decades, work life has undergone

great changes. Not only work itself, but also our

opinion of work, has changed. Now we know that

a good work environment should not only be

healthy and safe, but should also encourage per-

sonal and professional development, job satisfac-

tion and personal fulfilment, all of which

contribute to improved work quality and product-

ivity. We know that the way work is organized is of

importance, and that the situation in the labour

market affects the work, the worker and the work-

er’s health and well-being. So, there are different

aspects of this development of work life. One of

the most important and common occupational

health problems today is ‘stress’.

Stress, downsizing of companiesand unemployment

In a recent study on stress symptoms, ‘a feeling of

general irritation’ was found to be most common,

followed by headaches, depression and sleep diffi-

culties. On questioning workers on which were the

eliciting stress factors, ‘high workload’ was the

most common response, followed by ‘short deliv-

ery times’, ‘no influence at work’, ‘no support from

manager’, ‘long working hours’ and ‘worry about

job security’.

During the 1990s, especially during the first half

of the decade, general welfare in many countries

was influenced by a severe, world-wide economic

recession. Many companies had to downsize and

unemployment rates increased dramatically.

It is well known that unemployment is trau-

matic. However, workers still in employment also

suffer the effects of high rates of unemployment.

Thus, as a consequence of the recession, enter-

prises downsized and work pace and work stress

increased. Nobody complained because of the risk

of job loss. Paradoxically, rates of sick leave dimin-

ished – when workers were sick, they nevertheless

went to work because of fear of losing their job.

During the late 1990s, the labour market in many

countries recovered and the rate of unemployment

fell steadily; unemployment has now reached

a politically acceptable low level. However, the

latest statistics on reported work-related injuries

and diseases show a marked increase. Among the

work-related diseases, those indicated to be caused

by organizational and social factors have increased

the most, and considerably more than one-half of

these cases are attributed to stress.

Lessons from the past – challengesfor tomorrow

It is interesting to note the observations of a

historian on this subject (Johannisson, 2001).

The changing work life

Stress, downsizing of companies and unemployment

Lessons from the past – challenges for tomorrow

Men and women at work

Child labour

The integrated occupational health concept

But don’t forget the ‘old’ and well-known hazards

New areas coming into focus

Occupational health – today and prospects for tomorrow

6

Johannisson points out the similarities between the

symptoms of what we see happening today among

employees suffering from stress and what hap-

pened 100 years ago in the transition phase be-

tween the farming and industrial societies. Today

we are living through transition: one between the

industrial society and the information and com-

puter technology (ICT) society. In both cases,

large population groups have to adapt to work

life skills and experiences that are quite new,

which may be difficult for many of us without

proper education and training, and which may

result in stress reactions.

So, what is the remedy today for stress at work?

Let me quote a former Director General of the

Swedish Social Insurance Board (Sherman, 2002).

. . . the increased stress and sick leaves are a reaction of

what happened in the 1990s when companies were

‘slimmed’, and work intensities increased. Nobody

could expect me to believe that the 325 000 employees

more on sick leave today than five years ago, are sick

in an objective sense. This does not mean that they

should be sent back to work, unless we change the

work itself. Burn-out and stress are symptoms of a dis-

eased society, where people have been pressed over their

capacities.

I agree with Sherman and hope that society will

take prompt measures to start recovering from its

disease.

Men and women at work

We know today that women –more thanmen – are

frequently affected by injuries and sickness caused

by a poor work environment. In recent years, the

prevalence of stress-related health problems has

increased markedly among women in particular.

This gender difference is linked to women’s chan-

ging roles and greater participation in the paid

workforce, without a corresponding reduction in

unpaid work (household work, child care, etc.).

Furthermore, regardless of country and continent,

women are paid between 5% and 50% less than

men are paid for the same work. The situation was

summarized at the ‘Work, Women and Health’

Conference in June 2002 as follows (Lundby

Wedin, 2002): ‘Everywhere you turn in the world

you will find that it is the women who are the

poorest, who have the lowest wages, who have

the worst working environment and who get the

worst pension deals’.

We need more data to describe women’s and

men’s working conditions. Women often have a

mixture of illnesses and so-called vague symptoms

such as fatigue, reduced vitality, feelings of insuf-

ficiency, different pains and discomfort. These

symptoms are associated with psychological

causes and, up until now, according to some re-

searchers, they have not been taken as seriously as

other somatic symptoms. In turn, this means that

women’s health problems at work are not as visible

as those of men, and, as a result, they are neglected

both in research and in practice.

Child labour

Child labour has been, and still is, a world-wide

problem. Involuntary underage workers typically

forfeit the chances of developing knowledge and

gaining education as other children do, and they

risk their health and welfare, under duress, in the

cause of commercial gain for others or simply for

their own and their families’ survival.

An example comes from Bangladesh, where

child labour is a rapidly growing phenomenon of

concern (Rahman, June 2002, Institute of Child

and Mother Health, Bangladesh). The total num-

ber of children in labour approaches seven million,

i.e. 20% of the total child population aged 5–14

years, of whom 96% are employed in informal

sectors. Most of the children are compelled to

engage themselves in dangerous and hazardous

occupations, and many of the children suffer

from injuries. In the Bangladesh study (covering

the transport sector and small metallic manufac-

turing enterprises), the 1-month prevalence mor-

bidity was almost 40%, and the proportional

morbidity from injuries was almost 50%. Cutting

of finger/hand constituted 52% of the injuries,

fractures 8%, sprains 9% and bruising 14%. In

total, 40% of these injured children did not receive

any kind of treatment, 23% consulted doctors and

13% were sent to hospital.

Global strategies and trends in occupational health: well-being at work in focus

7

This study is referred to in detail to show the

magnitude of the problem, and to show how self-

evident it must be for all international occupa-

tional health organizations to engage themselves

wholeheartedly in the fight against child labour.

Furthermore, it is important to understand how

the meaning of the word ‘well-being’ varies

according to whether you happen to be born in a

rich or a poor country.

The integrated occupational healthconcept

At the beginning of the twentieth century, occupa-

tional health was a matter for physicians. By and

by, however, new groups became involved: nurses,

engineers and hygienists. Today, topics within

ergonomics and work organization are included,

and the ‘integrated’ occupational health area even

extends to labour market issues.

It is easy to understand the inter-relationships

between medicine, hygiene and ergonomics. Work

organization defines the contents of the work and

how it is distributed among the employees (‘right

person for the right work’). ‘Theoretical’ work

organization encompasses, for instance, where

and when the employee comes in the decision hier-

archy; possibilities for lifelong learning; and evalu-

ation of workloads and risks for ill health. More

practical ‘projects’ may include ‘stress and health’,

‘conditions for human service work’, ‘industry and

the human resource’, ‘gender and work’, ‘lifelong

learning’ and ‘work and culture’.

Labour market issues are somewhat more per-

ipheral, however important for the employee. Ex-

amples of practical projects are ‘job creation’,

‘labour law’ and ‘social economics’. Some of the

labour market topics overlap with work organiza-

tion, which in turn overlaps with ergonomics,

which in turn overlaps with medicine, etc.

There are reasons to believe that the integrated

occupational health concept will play a leading

role in the future. The development in work life

matters within the European Union (EU) points in

this direction. Employability, entrepreneurship,

adaptability and equal opportunities are the four

‘pillars’ in the EU 1998 guidelines.

But don’t forget the ‘old’and well-known hazards

It can readily be seen from the above that occupa-

tional health today is a growing field, covering a

wide range of different topics, in which research,

practice and prevention go hand in hand. Overall,

in addition to stress, musculoskeletal diseases

and asthma and other allergies are the most preva-

lent work-related diseases, while fatal accidents

at work still claim a large number of lives each

year world-wide.

However, we must not forget that there are one

million different chemical compounds in our

immediate environment; several hundred new

chemicals are introduced each year into the envir-

onment; the long-term toxicity of extremely low

concentrations of these chemicals is unknown.

New work technologies mean exposure to ‘new’

physical factors, such as electromagnetic fields

(EMFs), the full effects of which we do not know.

Recent assessments by the International Agency

for Research on Cancer (IARC) now classify

low-frequency EMFs as possible risk factors for

childhood leukaemia, and the health risks of

using mobile phones are under evaluation.

Infections constitute another important health

area, and special emphasis is directed, for self-

evident reasons, towards the HIV/AIDS epidemic.

Forty million people in the world are now infected

[‘what we nowwitness is a world historic epidemic

larger than the Black Death and the Spanish flu’

(Kallings, July 2002, Secretary General, Inter-

national AIDS Society)], and in some parts of the

world (sub-Saharan Africa, Eastern Europe and

South-East Asia) the epidemic is still spreading.

The consequences of the epidemic in the most

affected countries are devastating; the workforce

is dying, national production is falling, the level of

education is declining and poverty is increasing. It

is quite clear that one of the main missions of

occupational health workers world-wide has to

be the prevention of this epidemic. Promising

workplace interventions including education

about preventing transmission have been imple-

mented in some of the sub-Saharan Africa coun-

tries, and services have also been extended to the

wider community. But more has to be done.

Chapter 2

8

New areas coming into focus

As mentioned, work life is undergoing a process of

continuous change. New ‘problem’ areas can be

expected come to the fore. Some of these may

always have existed but, for various reasons, been

ignored by society not out of any ill-will, but per-

haps simply out of ignorance. Three such areas are:

� sexual harassment;

� physical violence; and

� bullying.

All of these are in some way related to each

other. Recent studies conducted by the European

Foundation for the Improvement of Living and

Working Conditions (under the European Com-

mission) have shown these problems to be rela-

tively common; the prevalence of the first two

has been estimated to be between 5% and 10%,

and the prevalence of the last (bullying) between

10% and 15%.

Occupational health – todayand prospects for tomorrow

Since the mid-1990s there has been a decline in

occupational health activities in many ‘developed’

countries. The main reason has been a world-wide

economic recession leading to ‘slimmed’ national

budgets and increasing unemployment rates, with

occupational health services (OHS) being one of

the first areas to suffer. An additional contributing

factor could be the increasing age of those who

work within OHS and, consequently, an increasing

number of people have retired and have not been

replaced. Yet another factor of possible import-

ance is ‘the changing world of work’, with a tran-

sition from an industrial society to an ICT society,

with OSH still being largely considered a function

of industry.

However, there are signs pointing in the right

direction. In many countries, for instance, there is

a political revival of positive interest in OHS. Fur-

thermore, organizations such as the ICOH (Inter-

national Commission for Occupational Health)

are attracting new, young members from different

parts of the world. With what we have today, there

are reasons to be positive about the future. Work

life is constantly changing, which is nothing but a

challenge for OHS working for health and well-

being at work.

Global strategies and trends in occupational health: well-being at work in focus

9

Part 2

Organ structure and function and the adverseeffects of work

Chapter 3

The structure and function of the lungs

J. Malcolm Harrington and Anthony J. Newman-Taylor

Introduction

The primary function of the lungs is to secure the

exchange of gas – oxygen and carbon dioxide –

between air and blood. The structure of the lungs

enables this function by conducting air through a

series of branching tubes (bronchi) to the sites of

gas exchange, the alveoli.

Structure

The lungs are composed of a number of topo-

graphical units called bronchopulmonary seg-

ments, which are roughly pyramidal in shape,

with their apices directed inwards and their bases

lying on the surface of the lung. Each lung is com-

posed of 10 such segments grouped together into

lobes. The right lung has three distinct lobes:

upper, middle and lower; the left lung has two

lobes, with a rudimentary third lobe (the lingula)

incorporated into the upper lobe. Each lower

lobe contains five segments: the right middle

lobe (and the lingula), two; and the upper lobes,

three.

The airways

Air is conducted into the lungs through a system of

branching tubes. The first of these is the trachea,

which is attached above to the larynx. It is a tube

about 15 cm long, lying directly in front of the

oesophagus, and held open by C-shaped rings of

cartilage in its walls. At the back, it is joined to-

gether by a sheet of muscle fibres (the trachealis

muscle), which, by contraction, reduce the diam-

eter of the tube. The muscle can prevent overdis-

tension of the trachea when the internal pressure is

raised, for example during the act of coughing.

The trachea divides into the left and right main

bronchi, which themselves branch into the seg-

mental bronchi (Fig. 3.1) and further branching

continues within each segment. A bronchus is de-

fined as an airway that contains cartilage within its

walls; divisions of the airways that contain no

cartilage are termed bronchioles. The smaller

bronchi contain less cartilage in their walls than

do the trachea and the large bronchi. Their walls,

and those of the bronchioles, are supported by

elastic fibres and also by dense connective tissue.

Moreover, they have two spiral layers of smooth

muscle fibres surrounding their lumen, which

Introduction

Structure

The airways

The acinus

The consequences of branching

The alveolus

The blood–gas barrier

The lining of the airways

The blood supply to the lungs

Lymphatics

The pleura

Function

Ventilation

Gas transfer

Blood–gas transport

Factors influencing lung function

Age

Smoking

Other functions

Occupational lung disease and disordered function

Further reading

13

contract under the influence of nervous (or other)

stimuli, thus lessening the calibre of the airway and

altering the rate of flow of air into and out of the

lungs.

It is usual to describe an airway in terms of the

number of divisions, or generations, which separ-

ate it from themain bronchus. The segmental bron-

chus is counted as the first generation, and its first

branch as the second generation, and so on. In this

classification, the bronchi comprise about 15 gen-

erations, the first five of which are ‘large’ bronchi,

having a plentiful supply of cartilage in their walls.

The sixth to fifteenth generations are ‘small’ bron-

chi whose walls contain only a sparse amount of

cartilage. There are some 10 generations of bron-

chioles, whose walls do not contain cartilage,

which ultimately open into the alveolar ducts

from which the alveoli originate. The bronchiole

that opens into the alveolar duct is defined as a

respiratory bronchiole, the one immediately prox-

imal to it as a terminal bronchiole.

The acinus

The acinus is that part of the lung distal to a

terminal bronchiole. It includes up to eight gener-

ations of respiratory bronchioles and their associ-

ated alveoli. It is approximately 0.5–1 cm in

diameter.

The lobule is the term used to describe the three

to five terminal bronchioles, together with their

acini, which cluster together at the end of an air-

way (Fig. 3.2).

The consequences of branching

The consequence of branching within the airways

is to greatly increase the total cross-sectional area

of the airways, decreasing the rate of airflow

through them. By the time air has reached the

terminal bronchioles, bulk flow of air has ceased,

leaving diffusion down concentration gradients as

Larynx

Cartilagerings

Trachea

Mainbronchi

Segmentalbronchi

Figure 3.1 The main airways.

TB

TB

RB2

RB3

RB1

Acinus

Lobule

Figure 3.2 An acinus. TB, terminal bronchiolus; RB, re-

spiratory bronchiolus. Note that RB has several generations

(RB1, RB2, RB3, . . . ).

14

Chapter 3

the means of transport. This has relevance and

importance for dust deposition. This is well illus-

trated by the data in Table 3.1.

The alveolus

The alveolus is the part of the lung in which gas

exchange occurs. There are 200–600 million al-

veoli in the fully developed adult lung, which

offer a surface area of some 100---200m2 over

which gas can diffuse. The alveolus is about

250 mm in diameter and its walls are lined with

two types of epithelial cells: the type 1 and type 2

pneumocytes. The alveolar wall is typically less

than 0.5 mm thick, but the epithelial lining is con-

tinuous throughout, and is composed of the cyto-

plasm of the pneumocytes. The alveolar wall is

surrounded by, and in intimate contact with, the

endothelial cells of the capillaries of the pulmonary

vascular bed (Fig. 3.3).

The type 1 pneumocyte is a large flat cell (like a

fried egg!), covering a much greater area of the

alveolar wall than the type 2 cell, although it is

less numerous. The type 2 cell, which is usually

found in corners of the alveolus, is a small cell

containing characteristic lamellated inclusion bod-

ies within its cytoplasm. These inclusion bodies are

the origin of surfactant, a lipoprotein that lines the

surface of the alveoli and acts to stabilize their size.

The alveoli may be thought of as small bubbles, the

surface tension of which is inversely related to the

radius. The forces acting to keep the alveolar ra-

dius constant are less than one would predict, due

Table 3.1 Cross-sectional area of the airways and rate of

airflow.

Area (cm2) Flow rate (cm s�1)*

Trachea 2.0 50

Terminal bronchioles 80 1.25

Respiratory bronchioles 280 0.36

Alveoli 10---20� 105 Negligible

*For a volume flow of 100ml s�1.

Normal

Endothelialcell

Type 1epithelial cell

Macrophage

AIR

AIR

Type 2epithelialcell

Figure 3.3 A section of alveoli, show-

ing the relationship between the vari-

ous cell types.

15

The structure and function of the lungs

to the presence of surfactant, which reduces the

surface tension within the alveolus. A number of

other cells are also encountered within the alveoli,

including connective tissue cells, blood cells and

phagocytes, called alveolar macrophages, which

are present in the alveolar space and may contain

carbon pigment taken up from the smoke-laden

air. The walls also contain elastic and collagen

fibres, which provide support. Having taken up

foreign material, macrophages travel up the air-

ways aided by the cilia in the epithelial lining (see

below) or are cleared via the lymphatics from the

centre of the acinus. Upon reaching the larynx,

they and their contents are usually swallowed but

with mucus hypersecretion may be coughed out.

Foreign material cleared from the lungs and swal-

lowed may be subsequently absorbed from the gut.

The blood–gas barrier

The epithelial lining cells of the alveolar wall, to-

gether with the endothelial cells of the capillaries

(each with their own basement membrane) and the

tissue fluid in the spaces between, make up what is

known as the blood–gas barrier. This is the ‘thin’

side of the alveolus where the basement mem-

branes of type 1 epithelial cells and capillary endo-

thelial cells are fused. It is the distance that gas

molecules, or indeed any other material, must

cross when passing into or out of the alveolus.

The total distance involved is probably less than

0.001 mm.

The lining of the airways

The airways are lined with a ciliated epithelium

that contains a number of different types of cell

(Fig. 3.4). In the large airways, the epithelium is

pseudostratified, that is, it has the appearance of

being composed of more than one layer. This is due

to the fact that the basal cells do not reach the

surface of the epithelium, although all the other

cells do reach the basement membrane, which is a

permeable layer of material synthesized by the

cells, acting to stick the cells together. In the smal-

ler airways there is only one layer of cells, each of

which reaches the surface. The goblet cells secrete

mucus, which spreads out to form a layer on the

surface of the airway where it traps particulate

matter. Mucus is also secreted by the submucosal

glands and is constantly being moved up towards

the larynx by the synchronous beating of the cilia,

carrying with it material trapped in the airways,

together with the alveolar macrophages containing

material scavenged from the alveoli. This so-called

mucociliary escalator is the most important mech-

anism through which the airways are cleared of

particulate matter. Ciliated cells are found down

AE

D

CB

Figure 3.4 The epithelial lining of the

trachea, with its various cell types.

A, basal cell; B, non-ciliated cell;

C, brush cell; D, goblet cell (secreting

mucus); E, ciliated cell.

16

Chapter 3

as far as the respiratory bronchioles so that this

mechanism operates continuously from the

bronchiolo-alveolar junction to the larynx.

The function of the brush cells is unclear at pre-

sent, but the structure and dimensions of themicro-

villi on the surface of the cells, from which they

take their name, suggest that they could be con-

cerned with the absorption of fluids from the air-

ways and hence with the control of fluid balance.

The blood supply to the lungs

The lungs have two arterial blood supplies and two

sets of venous drainage. Their arterial supply is

from the pulmonary and bronchial arteries,

whereas venous blood is conducted away by the

pulmonary and bronchial veins.

The left and right pulmonary arteries arise from

the right ventricle of the heart and convey to the

lungs blood that has been returned from the tissues

into the right atrium. Thus, blood in the pulmon-

ary arteries, unlike blood in other arteries, has a

low partial pressure of oxygen. It is also under

much less pressure than blood in the other arteries,

the pressure in the pulmonary artery being about

one-tenth of the pressure in the systemic arterial

circulation.

Both airways and blood vessels are low-

resistance systems that enable an equivalent flow

of air and blood to either side of an alveolar capil-

lary. The pulmonary artery supplies the capillary

bed surrounding the alveoli and at any one time

approximately 80 ml of blood is in contact with

the alveolar air (out of the total of 400 ml in the

pulmonary capillary circulation). The pulmonary

artery divides with each airway divide but, in add-

ition, other arteries arise to supply the alveoli

around the airway. These additional arteries are

called the supernumerary branches and outnumber

the so-called conventional branches by about three

to one.

The pulmonary veins run at the periphery of the

bronchopulmonary segments and return blood

with a high partial pressure of oxygen to the left

side of the heart, where it is pumped into the

systemic circulation.

The bronchial arteries are branches of the aorta

and supply oxygenated blood to the capillary beds

in the walls of the airways. Blood from the capil-

laries drains back through the pulmonary veins,

and the bronchial veins receive blood only from

the large airways, the lymph nodes and the pleura,

which they convey to the azygos vein for return to

the right atrium.

Lymphatics

Lymph vessels convey interstitial fluid from the

tissue spaces back to the thoracic duct, which

opens into the left internal jugular and subclavian

veins. After themucociliary escalator, this drainage

system from the centre of acini is the second major

route by which alveolar macrophages, laden with

dust particles, leave the lung. The lymph vessels

drain at intervals through lymph nodes, whichmay

be regarded, simply, as filters which trap particu-

late matter travelling in the lymph. Cells present in

the lymphmay also be arrested in the lymph nodes,

and if these cells happen to have broken away from

a tumour developing within the lung, they may

divide and multiply within the nodes, causing

them to enlarge.

Lymph vessels are abundant in the pleura, the

connective tissue septa between the bronchopul-

monary segments, and in the walls of the airways

and blood vessels; they do not appear in the walls

of the alveoli. The lymph drains from the periphery

towards the hilum of the lung and through the

nodes situated there (Fig. 3.5).

The pleura

The lungs are completely covered by a fibroelastic

membrane called the visceral pleura. Lining the

inside of the thoracic cavity is a complementary

membrane, the parietal pleura. The opposing

pleural faces are covered with a layer of cells that

secretes a serous fluid into the space between them.

This fluid acts as a lubricant between the two

pleural layers and allows the lungs to move easily

over the parietal pleura during respiration.

The two pleural layers are continuous around

the root of the lungs (Fig. 3.6). The space between

the two layers of pleura is known as the pleural

cavity and under normal conditions it contains

only a thin film of fluid. For this reason, it is only

17

The structure and function of the lungs

a potential space, although under some abnormal

conditions it may become filled with fluid, and

thus become a real space.

Function

Only a brief outline of lung function is provided

here. Emphasis is placed on the main aspects of

pulmonary function and on the more commonly

used measures. Patterns of disordered function

that are characteristic of the commoner occupa-

tional lung diseases are appended. More extensive

reviews of the subject are listed at the end of the

chapter.

The main function of the lungs is to allow ex-

change of gas between air and blood. Oxygenated

blood is transported to tissue via the arterial sys-

tem. Oxygen is carried in the red blood cell pri-

marily by the haemoglobin, whereas carbon

dioxide is transported from the cells using both

the same mechanism and dissolved in the blood.

The lungs, therefore, act like a bellows, transport-

ing oxygen in the air to the alveoli where it is

exchanged for carbon dioxide. The blood leaving

the lungs via the pulmonary veins has a higher

oxygen concentration and a lower carbon dioxide

concentration than the blood entering the pulmon-

ary arteries. The rate of ventilation controls these

concentrations within narrow limits in the pres-

ence of wide variations in the demand for oxygen

and for the removal of carbon dioxide by respond-

ing to and maintaining the partial pressure of

carbon dioxide (Pco2) in blood.

The pathway from air to tissue involves several

steps. First, the air has to reach the alveolar–

capillary membrane, where oxygen crosses to

reach the red blood cell. The final step is the uptake

of oxygen by tissue cells from the circulating

blood. Carbon dioxide is transported in the oppos-

ite direction. This chapter is mainly concerned

with the first two steps in the pathway.

The propelling force for the first step is the

cyclical pressure changes produced in the lungs

by ventilation, which is itself controlled by the

respiratory muscles. Inspiration is an active pro-

cess, achieved primarily by the contraction of the

diaphragm and the intercostal muscles, which

overcomes the resistance of the lungs. Resistance

to these pressure changes comes from the conduct-

ing airways themselves and from the elasticity of

the lung and chest wall tissues. Expiration occurs

passively. Disordered ventilatory function can be

due to respiratory muscle weakness, stiff lungs

(decreased lung compliance) or narrowed airways.

The second step, diffusion across the alveolar–

capillary membrane, is short compared with the

first step (300mm compared with 50 cm). How-

ever, gas transport can be disrupted at this stage by

thickening of the alveolar–capillary membrane as

occurs in diffuse pulmonary fibrosis. Such thicken-

ing impedes the flow of oxygen and carbon diox-

ide, which is governed by the partial pressure

differences of these two gases across the mem-

brane. As carbon dioxide is much more water sol-

uble than oxygen, the main effect of such fibrosis is

failure to transport oxygen. Carbon dioxide reten-

tion in the body is much more likely to be due to

ventilation unmatched with perfusion caused by

ventilatory failure, more usually caused by airflow

limitation than pulmonary fibrosis.

Pulmonaryartery

Pulmonaryvein

Respiratorybronchiole

Pleura

Lymphatic

Bronchiole

Alveoli

Figure 3.5 A bronchopulmonary segment. The sizes of the

vessels and the airways are not to scale. Note that for clarity

the lymphatics are shown only on the right and the blood

vessels only on the left.

18

Chapter 3