Initial respiratory responses in welding apprentices.
Holcroft-C; Wegman-D; Woskie-S; Song-MY; Naparstek-R
NIOSH 2004 Dec; :1-61
Despite some inconsistencies in study results, evidence of an association between welding fume exposure and occupational asthma has been growing over the past 20 years. Most of the earlier epidemiological studies concerning welding exposures and respiratory effects have been limited by their cross-sectional study design, the selection of study populations with extensive welding experience, and limited information on the timing and nature of exposures to welding fumes. We conducted a study of 200 welding apprentices in which airway reactivity and acute respiratory responses were measured early in the apprentices' welding careers and six-month follow-up measures were collected. Promising findings from Fishwick et al. (1997) reported a drop in forced expiratory volume in one second (FEVl) I5-minutes after a welder's first daily exposure. To build on these findings, we measured pulmonary function tests (PFTs) at the start of a welding class, 15 minutes after welding and at the end of a 2-3 hour session for apprentices learning to weld in the second or third year of their training programs. Short-term changes in pulmonary function were matched with real time exposure measurements of particulates along with average levels of fluoride and NOx. First-year apprentices who did not take welding classes formed our comparison group. Baseline respiratory questionnaires and cold-air challenge tests for airway reactivity were administered for all participants at the beginning of the apprentice year and follow-up questionnaires and cold-air challenges were repeated at the end of the apprentice year. Although average exposure levels were well below permissible exposures limits, peak excursions of welding fume concentrations were observed. Apprentices were older than expected with a mean age of 30 years (minimum=18, maximum=53). Forty-seven percent of the first-year and 60% of the second/third-year apprentices were current smokers. Three percent had physician-diagnosed adult asthma. Approximately 10% had experienced a high exposure to gas or fumes that made him or her sick. Twenty-two percent of all apprentices reacted on either baseline or follow-up cold-air challenge tests. However a pattern in cold-air reactivity was not observed as some participants who were not reactive at baseline subsequently reacted at follow-up but a greater number who were reactive at baseline did not react again at follow-up. Changes in FEV1 across a welding session were examined in association with time-weighted average (TWA) exposure, cumulative exposure, first 15-minute interval TWA, first 15-minute cumulative exposure, number of peak exposures, TWA under peaks and cumulative exposures under peaks. The most significant associations with change in FEV1 were found with numbers of peak exposures and cumulative exposure under peaks. Findings from this study suggest that respiratory effects of welding are subtle to detect. Although anecdotally some apprentices reported respiratory irritation from welding, responses were difficult to document. Respiratory effects due to exposures in evening welding classes may be relatively little in comparison to earlier exposures on the job. Repeated cold-air challenge tests are rarely conducted in occupational epidemiology studies and further study is needed to evaluate the individual variability in test responses. Real time welding exposure measurements provided some insight into the variability of welding exposures and the potential effect of peak exposures on lung function. Baseline respiratory status is important to assess in apprenticeship populations when possible. Controls for welding exposures, ventilation and respiratory personal protective equipment (PPE), were well-known by training directors and instructors. Ventilation systems were installed in all of the welding shops we visited. Key factors for good ventilation system designs will help in designing future systems. When good ventilation is not available on worksites, respiratory PPE is recommended for welding exposures although not required in most situations under current OSHA regulations. However, the OSHA requirement for an employer-implemented Respiratory Protection Program when respirators are in use was observed to discourage the voluntary use of respirators.
Welders; Welding; Welding-industry; Occupational-exposure; Occupational-diseases; Bronchial-asthma; Fumes; Welders-lung; Epidemiology; Reproductive-system-disorders; Pulmonary-system-disorders; Lung-function; Ventilation-systems; Respirators
Christina Holcroft, ScD, Work Environment Department, One University Avenue, Lowell, MA 01854
Final Grant Report
Disease and Injury: Asthma and Chronic Obstructive Pulmonary Disease
National Institute for Occupational Safety and Health
University of Massachusetts Lowell, Lowell Massachusetts