Inadvertent ingestion exposure in the workplace

1 Health and Safety Executive Inadvertent ingestion exposure in the workplace Prepared by the Institute for Occupational Medicine for the Health and Safety Executive 2007 RR551 Research Report Health and Safety Executive Inadvertent ingestion exposure in the workplace Phase I Literature review Y Christopher, S Semple, GW Hughson & JW Cherrie Institute of Occupational Medicine Research Park North Riccarton Edinburgh EH14 4AP Little is known about the relative importance of Inadvertent ingestion of hazardous substances from work activities. In this report we review the available scientific literature to help understand whether Inadvertent ingestion is an important route of exposure and for which agents.

2 Proposals are made for a conceptual model of the processes involved with this type of exposure and for possible exposure metrics to be used for workplace measurement. This is the first of three reports dealing with Inadvertent ingestion exposure in the workplace . This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy. HSE Books Crown copyright 2007 First published 2007 All rights reserved.

3 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) without the prior written permission of the copyright owner. Applications for reproduction should be made in writing to: Licensing Division, Her Majesty s Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by e-mail to ii CONTENTS SUMMARY V 1 INTRODUCTION 1 2 IDENTIFICATION OF SUBSTANCES AND TASKS WHERE ingestion exposure MAY BE SIGNIFICANT 3 Introduction 3 Metals 3 Pharmacologically active agents 3 Infectious agents 4 Radionuclides 5 Relevance of ingestion exposure to allergens 5 3 HOW MIGHT PEOPLE BE EXPOSED BY Inadvertent ingestion 7 Scope and terminology 7 Development of a conceptual model of Inadvertent ingestion exposure 7 The role of hands and objects in transferring contamination to the

4 Mouth 9 4 RELEVANT exposure METRICS FOR ingestion 11 5 DISCUSSION 13 6 REFERENCES 15 iii iv SUMMARY Human exposure to hazardous substances in the workplace by inhalation and skin contact are well understood, but there has been little systematic research into ingestion of hazardous substances used at work. This report attempts to identify from published information whether Inadvertent ingestion is an important route of exposure in the workplace and examines possible methods that could be used to quantify ingestion exposure .

5 A number of papers highlight jobs and substances where Inadvertent ingestion may be important, typically through case reports or from a theoretical analysis. These scenarios involve exposure to some metals or metal compounds, pharmaceuticals, pesticides, some infectious agents, unsealed radioactive sources and some high molecular weight allergens. A conceptual analysis of Inadvertent ingestion exposure highlights the role of hand-to-mouth and object-to-mouth events as the primary exposure processes. Two exposure compartments are defined: the peri-oral area ( the area of skin around the outside of the mouth) and the oral cavity.

6 Several options are highlighted for exposure -related measurements, including peri-oral wipes, saliva samples, mouth-rinse samples, hand-wipes and under-nail scrapings. Human behaviour has a key role in determining Inadvertent ingestion exposure . For example, some people are habitual nail biters or repeatedly touch their mouth, both of which will increase the chance of ingesting contaminants on their hands. The frequency that people touch their face is dependant on the circumstances of their work and probably the degree of psychological stress they are under.

7 A proper understanding of the importance of these factors will help in designing interventions to reduce the risks from ingesting hazardous substances at work. When making inhalation or dermal exposure measurements we recommend that details of personal behaviours should be recorded so that some estimate of ingestion risks can be inferred. This is the first volume of three reports that describes the results of a programme of research to investigate Inadvertent ingestion . v vi 1 INTRODUCTION For chemicals to have a toxic effect on the body they must first pass across a functional barrier separating the environment from the internal organs.

8 Most textbooks that deal with human exposure contain a description of the routes of entry for chemicals into the body, commonly: inhalation with the barrier being the lining of the lung; dermal absorption with the stratum corneum as the barrier and ingestion with the wall of the gastrointestinal tract as the barrier (Dinman and Dinman, 2000). Inhalation exposure is invariably singled out as the most important route in terms of potential to cause toxicity, followed by dermal contact with chemicals and then ingestion .

9 The assessment of exposure to chemicals in the workplace has tended to focus primarily on inhaled material. Mines, smelters, cotton mills and many other manufacturing processes traditionally produced large quantities of airborne dusts, gases and vapours that were generally poorly controlled and often damaged workers lungs or induced other target organ toxicity from absorption through the lungs into the blood. During the last decade occupational exposure research has focused more on the potential for chemicals to pass through the unbroken skin and the need for greater understanding and control of dermal exposure has been highlighted (Dost, 1995) The importance of the ingestion route of exposure has tended to be considered unimportant.

10 This is likely to be due to a number of reasons: 1. the common belief that ingestion of chemicals can only occur by intentional means or acts of gross negligence, and hence can be avoided; 2. the recognition that many materials are only very poorly absorbed from the gut ( they have low bioavailability) and as such are unlikely to produce toxic effects when swallowed in small quantities; 3. the presumption that where a worker is exposed by inhalation, dermal contact and ingestion , the mass of material taken into the body by ingestion may be small in comparison with the other routes.