Criterios para establecer indicadores de gestión

There are basically three stages in furniture making though the nomenclature may vary from place to place. These are: conversion, component making and assembly. Conversion involves sawing, planning and chipping. Exposure to dusts may occur especially if local exhaust ventilation is not used. Component making involves cutting converted pieces of timber to finished sizes and machining into the components needed to make furniture. Exposure to dusts could be high at this stage.³² Assembly could involve exposure depending on whether sanding is done at

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this stage or not. Cabinet making is a highly skilled trade closely related to furniture making.³³

2.4 FACTORS INFLUENCING OCCUPATIONAL EXPOSURE TO WOOD DUSTS

The wood work processes performed by a particular group of individuals determine the level of exposure as described above. The harder the wood, the more lightly bound are the particles. Therefore, more shaking occurs with hard woods, resulting in more dust. Cells in dry wood are less plastic and more likely to be shattered, leading to dust formation. While the moisture content of different species of tree varies; it is also influenced by the freshness (greenness) of the wood. Drying is another processing of wood. It may change the chemical composition of wood. Some of the relatively low molecular mass extractives such as monoterpenes may be volatized.³⁴

The volume of dust generated also depends on how the processing of wood is carried out. Wood working machines have increased greatly in

efficiency and the increased speed of production has resulted in the generation of more dust. Machines also generate finer dust particles.

A number of characteristics of the work place may also affect the level of wood working machinery and the regulatory environment. Small work places may have fewer engineering controls in place. The quality and methods used for cleaning are

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important, because wood dust that has settled on the floor and equipment may become re-suspended.³⁴

Endotoxins (lipopolysaccharide protein complexes, which are integral part of gram-negative bacteria) and allergic fungi are the main biohazards found in wood processing workplaces.³⁵ Chest tightness, cough, shortness of breath, fever, and wheezing have been observed in workers exposed to airborne endotoxins.³⁶ Endotoxins may be an important causative agent in the development of chronic bronchitis associated with organic dust exposure.³⁶ Exposure to wood dust can modulate the expression of macrophage derived cytokines and chemokines.³⁷ Early allergic reactions to coniferous wood and to microorganisms associated with wood dust are common among sawmill workers, posing a potential risk of work-related disease in this occupational group.^{38, 39}

2.5 VENTILATORY DYSFUNCTION FOLLOWING WOOD DUST EXPOSURE TO LUNGS

Studies have shown that breathing wood dust can be hazardous to health.8,9,14,32,38

High prevalence of respiratory symptoms principally cough, chest pain and sputum production among sawmill workers has been reported in South Western Nigeria³⁹ In this south western Nigerian study, the pulmonary function parameters were significantly lower (p<0.05) in the sawmill workers than controls. A large number (94.9%) of the workers were aware of the potential hazards of exposure to saw dust while less than 20% wore protective masks.³⁹

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Respiratory symptoms were common during the working hours among the saw mill worker’s and the prevalence of respiratory symptoms

was noticed to be strongly dependent on the duration of exposure.³⁹ The prevalence of chronic cough increased from 5.8% in workers with less than 2 years exposure to 33.3% in those with over 10 years of exposure.

Dyspnoea was not seen in those with less than 2 years of exposure but showed an upward trend with increasing years: It was 1.9% in those with 2.5 years exposure and 25% in those with over 10 years exposure. Prevalence of nasal catarrh was found to be between 15.0% and 41.7%. Asthmatic symptoms showed the same pattern; 1.9% in those with 4 years exposure, 15.0% in those with between 6-10 years and 33% in those with over 10 years exposure. Overall, chronic cough occurred in 11.1%, dyspnoea in 3.3%, nasal catarrh in 19.0% and asthma in 5% of the workers,³⁹ in their study.

Abnormal Spirometric measurements were also found to be significantly lower in study subjects than in control subjects (FVC: 3.84 

0.8 versus 3.31  0.22, p< 0.01; FEV1 2.11  0.12 versus 2.45  0.31, p<0.01;

mid expiratory time (MET) in seconds: 0.89  0.8 versus 0.58  0.23 p < 0.01).

A cross sectional study of cedar workers, by Chang-Yeung et al.⁴⁰ reported that cough, dyspnoea, and asthma were more frequently among 652 western cedar wood workers than among 440 office workers. Impairment of

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respiratory function as measured by FEV1, FVC, forced mid expiratory flow (FMEF) was between 25 and 75% of FVC (FEV25‗75%) and FEV1/FVC significantly correlated (p < 0.001) with increasing length of employment in cedar mills. The odd ratios were adjusted for smoking, race and age.

Pisaniello et al.⁴¹ in a cross sectional south Australian study among 168 wood workers and 298 workers with no significant exposure to wood dust in furniture factories, reported that there is a significant association between exposure to hard wood dust with two or more nasal symptoms, after adjustment for smoking and age. Another study by Norish et al⁴² showed that symptoms of upper and lower airways were more frequent among 44 randomly selected wood workers than among 38 office workers.

Al Zuhair et al.⁴³found a significant decrease in FEV1 and FVC over the work shift period. This was also demonstrated among 60 workers in a furniture factory machine floor and cabinet shop.

A study among 145 non-smoking furniture workers and 152 non-smoking workers in a bottling firm with no exposure to dust in South Africa showed that cough, phlegm, dyspnoea, wheezing and nasal symptom were two or three times commoner in exposed than unexposed workers.⁴⁴ Spirometric measurements were significantly lower for exposed men than for unexposed. There was, however, no difference in these measurements between exposed and unexposed women, years

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of employment as a significant predictor of loss of lung function as measured by spirometric indices was also noted.⁴⁵

A cross sectional study by Schlunssen et al.⁴⁶ which included 54 furniture factories and three control non-furniture factories showed that Wood workers had increased frequency of coughing with negative interaction between dust exposure and smoking. A dose response relationship was also noted between dust exposure and asthma symptoms and a positive interaction for asthma was seen between female gender and dust exposure. Increased frequency of wheezing and across-shift decline in FEV1, among workers using pine wood was also observed, it was also noted that Wood dust exposure might cause respiratory symptoms, despite relatively low exposure.⁴⁷

The mean values of PEFR, MMF and FEF were significantly lower in the exposed workers than in the controls for both smokers and non smokers. The pulmonary function deficit with the exception of FEV1/FVC also showed a significant trend with increasing levels of wood dusts.^47-52

All parameters of pulmonary function were significantly lower in exposed workers than in controls and showed a declining trend with increasing exposure levels classified by job titles. These results also indicated that high level of wood dust exposure in the wood mill industries may lead to pulmonary hazards.⁴¹

2.6 DIAGNOSING OCCUPATIONAL LUNG DISEASES

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Recognition and early diagnosis of occupational lung disease could halt disease progression and would protect co-workers from continuous exposure to work place hazards. With the predicted increase in occupational disease in developing countries we need to have a high index of suspicion for diagnosing occupational diseases. Occupational lung disease can be diagnosed like any other diseases based on history of exposure to offending substance, duration of exposure, physical examination, lung function test, chest radiography, Computerized Tomography (CT) or contrast enhanced, Magnetic Resonance Imaging (MRI) and other ancillary investigations.

2.6.1 OCCUPATIONAL HISTORY

A lifetime occupational history is essential as some diseases like silicosis could manifest 10 years after exposure has ceased.⁵³ High risk occupations are those with obvious dust, smoke and vapor production while spraying, drying and coating of surfaces also carries a relative risk.³⁶ A history of worsening of symptoms as the work progresses and relieve of symptoms during off work period may suggest a relationship

between the occupation and disease process.^54,55,56 There will also be an associated increase in number of co-workers also manifesting with similar symptoms. ^57,58,59

The pattern of the disease process should also be identified to enable a clinician decide upon the possible etiological agents.⁶⁰ For epidemiological

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survey, questionnaires are important tools for data collection on symptomatology of the disease process.⁵⁹

2.6.2 PULMONARY FUNCTION TEST

Pulmonary function test is important aspects of evaluating lung diseases which cannot be over looked especially when the risk factors are evident.⁶¹ the major types of pulmonary function test include spirometry, measurement of lung volumes and quantification of diffusion capacities.

2.6.2.1 SPIROMETRY

This is a non invasive way of measuring expiratory flow rates which takes only 10-15 minutes. It is cost effective with no attendant risk.

The forced expiratory volume in one second (FEV1) is the most important spirometric variable for assessment of airflow obstruction. It declines in direct and linear proportion with clinical worsening. It also determines the degree of obstruction as mild, moderate or severe. The measured FEV1 is usually expressed as a percentage of the predicted for determination of normality.⁶² As a rough guideline, the predicted FEV1, for a 50 year old man of average height is 4.0 L and 3.0 L for a woman of the same age. There is usually a very gradual transition from normal lung function to mild airway obstruction. In order to improve sensitivity physiologist adopt FEV1/FVC ratio as a more sensitive index, which is

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usually expressed as a percentage, 70% being considered as the lower limit of normal.⁶²

2.6.2.2 PEAK EXPIRATORY FLOW RATE:

The peak expiratory flow is the maximum flow delivered during a forced expiration starting from a level of maximum lung inflation. It is an indirect way of assessing airway caliber though not a very sensitive tool of detecting mild airway obstruction.⁶³ It is however a good screening test for airway obstruction.

The peak flow meter is simple, portable, easy and convenient way of monitoring ventilatory function in field studies.⁶³

2.6.2.3 LUNG VOLUMES

Measurement of total lung capacity (TLC) may be useful when the vital capacity is decreased. For example in the setting of COPD with a low vital capacity, measurement of the TLC can help determine if there is a superimposed restrictive disorder.⁶¹

Methods of measuring TLC are:

- Helium dilution - Nitrogen washout

- Body plethysmorgraphy.

Measurement of TLC using chest X-ray correlates within 15% of those obtained using a body plethysmorgraphy.⁶⁴ The chest x-ray method is done by

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measuring the amount of air seen in the lungs, in a standard posterior-anterior and lateral views using a planimeter.

Chest x-ray though most times non specific gives a very good clue in detecting and monitoring occupational respiratory disease. For example the International Labour Organization (ILO) chest x-ray classification system for pneumoconiosis is based on the nature and size of the opacities seen and the extent of involvement of lung parenchyma. It is useful for screening large number of workers but this might underestimate or overestimate the impact of pneumoconiosis. Other diagnostic tools of importance in occupational lung disease may include, skin and serological tests, inhalational challenge tests, nasal lavage and bronchoscopy.

2.6.2.4 DIFFUSION CAPACITY FOR CARBONMONOXIDE

A test for the diffusion capacity of the lung for carbon monoxide (DLCO) is one of the most clinically valuable tests for lung function after spirometry. It is however very capital intensive. It measures the ability of the lungs to transfer gas from inhaled air to the red cells in the pulmonary capillaries. Patients with airway obstruction due to chronic bronchitis and asthma have normal DLCO while in emphysema, interstitial lung disease and pulmonary vascular disease, DLCO is reduced.

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CHAPTER THREE

3.0 MATERIAL AND METHODS 3.1 STUDY DESIGN:

This is a cross sectional study aimed at determining respiratory symptoms and ventilatory function among sawmill workers in Jos metropolis of Plateau State.

3.2 STUDY SITE:

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The study was carried out in Jos the capital city of Plateau state. Jos has an area of about 1,695 square kilometers and it is about 1250 meters above sea level, lying between longitude 8⁰ 53^/ and latitude 9⁰ 56^/. It has a population of about half a million people according to the 2006 population census (496,409).^67,68

Placed on the highland of the Plateau, the city enjoys climate that has made it a holiday city. Most of its inhabitants include the indigenous people of Plateau State and various ethnic groups from diverse parts of Nigeria and minorities of expatriates.⁶⁷ Majority of the people living in Jos are civil servants, business men, tourists, students, artisans and farmers.⁶⁸

3.3 STUDY POPULATION

There are four major timber sheds located within the city one is at Laronto market along Zaria road, another is off Murtala Mohammed way along Kirkasama road the other two are located in Bukuru area one at the building material market while the other one at the Bukuru market. There are also various woodwork shops scattered in various streets of the city where furniture works using wood is carried out on a daily basis. These wood workers have organized unions with leaderships, where they meet and discuss about new techniques, prices and security of their jobs.

Data collection was done during the day time from 8.00am to 4.00pm.

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The four major timber sheds within Jos metropolis were visited and the study populations were identified. Both verbal and written consent were obtained from their leaders and everyone who agreed to participate.

3.3.1 STUDY SUBJECTS

Study subjects were chosen from the population by simple random sampling method (lottery technique), using a table of random numbers where numbers were assigned to each of the subjects and numbers were picked at random. About 200 subjects were recruited for the and 25% of the subjects were selected from each timber shade irrespective of their section of work, this was because all the timber shades have equal size and approximately equal population density of workers.

3.3.2 CONTROL SUBJECTS

The control group comprised of staff of the Jos University Teaching Hospitalwho do not have any history of prolonged exposure to a dusty environment like cement, flour, tin mining, quarry or worked at cotton ginnery and have no chronic chest ailment, chest surgery or chest wall deformities like pectus excavatum, pectus carinatum, scoliosis etc. They were also matched for age, height and weight. They were selected through the same means as the study subjects.

3.4 SAMPLE SIZE:

There is no available study that documented the prevalence of respiratory symptoms in people exposed to wood dust in Plateau state. Previous researchers

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who carried out similar studies used sample sizes ranging between 59, 75 and 160 subjects the least prevalence was 0.15%. ^{14, 15}

The minimum sample size for this study was calculated by using this formula: ⁶⁹

N = Z² PQ /d²

N = Minimum sample size

Z = a constant which is 1.96 at 95% confidence interval P = Estimated prevalence which is 0.15%

Q = 1 – p

D = absolute precision which is 0.05 N = (1. 96)² X 0.15 X 0.85/0.0025=195

A round figure of 200 was chosen for the purpose of this study, 25% (50) of the total number was used as percentage attrition to cover for default and opt out cases.

3.5 STUDY CONSENT

The clearance for the study was obtained from ethical committee of Jos University Teaching Hospital, Jos, Nigeria. A signed or thumb-printed Informed consent (Appendix A) was obtained from sawmill workers and controls. All the participants were informed about their right to opt out at any time of the study if they desire to do so.

3.6 INCLUSION CRITERIA

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1. Sawmill and furniture workers who consented to the study.

2. Must have worked in the saw mill in Jos industry for at least six month.

3. Must have no other exposure to other dust like cement, flour or quarry.

4. Must be above 18 years of age.

5. Must not be a smoker.

3.7 EXCLUSION CRITERIA

1. All those with documented evidence of chronic chest condition Prior to employment.

2. All those not directly involved in any of the wood work processes elaborated in the discussion.

3. All individuals with history of sustained exposure to

substances known to induce bronchial hyper-responsiveness for example floor dust, cement dust etc.

4. Individuals unable or unwilling to perform pulmonary function test correctly.

5. Subjects with recent thoracic or abdominal surgery at least 6 Months before the study.

6. Individuals with cigarette related chronic lung disease were excluded from this study.

3.8 CONTROLS:

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Staff of Jos University Teaching Hospital were used for the study, eligibility was determined by excluding those with a history of repeated chest infection. For example a diagnosed chronic lung disease, smoking related chest diseases or those who have previously worked in a mining industry in the last 20years, those with chronic exposure to dusty environments like flour, cement and kaolin were also excluded, 200 of the staff consented for the study.

3.9 DATA COLLECTION

A history of occupational exposure to saw dust and previous respiratory symptoms prior to employment was taken from the participant, Physical examination was carried out, and anthropometric data was obtained. Weight (kg) and standing height (in meter) was measured using a stadiometer.⁷⁴ All Participants were asked to remove their shoes and heavy clothes so that only light and loose fitting clothes were used when measuring weight.

3.10 QUESTIONNAIRE

A Modified British Medical Research Council (MRC) questionnaire as adopted by Femi–Pearse et al ⁷⁰ in a Nigerian study, which is also used by American thoracic societywas used in this study. The results were expressed as percentages of predicted normal values for Nigerian men. The predicted values for women is always less than that of men at all ages in life .^{71 ,72}

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The FEV1 and FVC values were also expressed as percentages of predicted values for Nigerian adults using a regression equation by Anyanwu CH and Umeh BU, ^72,

Based on this questionnaire, the presence or absence of any symptom will be based on the following definitions as adapted by Femi- Pearse.⁷⁰

I. Cough and sputum are said to be present when the subjects have the symptoms either during work or after work.

II. Bronchitis is defined as presence of sputum with or without cough on most days of the month for as long as three consecutive months of the year, for at least two consecutive years.

III. Breathlessness is defined as the getting short of breath when walking with other people of the same age on level ground or up a short hill.

IV. Chest tightness is defined as feeling tight in the chest/difficulty in breathing on the first days back at work on more than 50% of occasions and /or on other days too.

V. Wheeze is defined as ability of subject or others nearby to hear a whistling sound when a subject is breathing.

VI. A non smoker is one who smoked regularly, but has since stopped for at least one month before the survey.

VII. A current smoker is one still smoking as defined even as at the time of survey.

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VIII. Pack years are calculated as number of cigarette smoked per day divided by 20 and multiplied by years of smoking.

IX. To include other types of tobacco, one cigarette is defined as equivalent to 1.25g pipe tobacco.

X. Rhinitis is said to be diagnosed if the subject answers “yes” to at least two nasal symptoms (rhinorrhea, Nasal itching, nasal congestion, or sneezing) at least 2 days a week.⁷³

XI. Atopy is diagnosed if the person has, currently or in the past, one or more of the following disorders according to the questionnaire atopic dermatitis, asthma, or perennial rhinitis

Additional questions on allergy asthma, family history of allergy, rhinitis, conjunctivitis, smoking habits, and occupation were also asked. Part of the questionnaire will address current job description, duration and location, and a detailed history of previous employment.

3.11 LUNG FUNCTION TESTING

A lung function assessment was carried out by means of a Wright peak flow meter. Computerized spirometer (Vitalography - Alpha spirometer 1994 model) was used to perform the lung function test (appendix c). The measuring maneuvers were carried out after full inhalation with maximum expiratory effort into the mouth piece of the instrument with no hesitation, cough or glottal closure during the procedure and without obstruction to the mouth piece. The

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