Epidemiological-environmental study of lead acid battery workers. III. Chronic effects of sulfuric acid on the respiratory system and teeth

Examination of potential sources of bias in the US Coal Workers' Health Surveillance Program

OBJECTIVES

We examined the potential influences of certain selection factors on the utility of the Coal Workers' Health Surveillance Program (CWHSP) data for tracking disease distribution and trends.

METHODS

We combined data from the CWHSP and the Energy Information Administration to examine any influence of variable worker participation on observed disease prevalence. We evaluated effects of differential participation by coal mining region, temporal changes in employment, and active surveillance efforts.

RESULTS

The published findings of pneumoconiosis distribution and trends from the CWHSP were robust compared with the various participation factors that might have affected their validity for population-based estimates of disease burden. Exploration of factors that could potentially bias the findings generally led to small increases in the primary estimates, mostly for the early years of the program.

CONCLUSIONS

We confirmed previously reported findings that there was a high prevalence of coal worker pneumoconiosis (CWP) around 1970-1974, a substantial decline in 1995-1999, and indications of an increase since then. Overall our findings suggest that the previously reported distribution and trends in CWP prevalence were broadly accurate.

The effect of the use of NP305 masks in improving respiratory symptoms in workers exposed to sulfuric acid mists in plating and pickling units

Background:

Plating and pickling processes are the most effective ways for increasing the strength of metal structures, and workers in these units are exposed to various contaminants, including acid mists. The aim of this study was to investigate the effect of protective masks in decreasing the respiratory symptoms and the aerobic capacity of workers that are exposed sulfuric acid mist.

Methods:

This interventional study was based on National Institute for Occupational Safety and Health (NIOSH) standard 7903 in which silica gel tubes are used for sampling the air in plating and pickling units for eight hours. After the samples were acquired and prepared, they were analyzed by ion chromatography and were compared with the American Conference of Governmental Industrial Hygienists (ACGIH) exposure limits. Respiratory symptoms were evaluated among two sets of test subjects, i.e., those who used NP305 masks in the workplace and those who did not use the mask.

Results:

The results showed that the concentration of sulfuric acid mist in the plating units was greater than the exposure limits, and concentrations at this level can cause an increase in symptoms related to irritation of the airway and a slight decrease in respiratory capacity. In this study, smoking had no significant effect on the severity of pulmonary dysfunction.

Conclusion:

The results indicated that the use of an NP305 mask is effective for decreasing symptoms resulting from exposure to sulfuric acid mist and improving respiratory capacity.

Dental erosion and sulfuric ion exposure levels in individuals working with sulfuric acid in lead storage battery manufacturing plant measured with mouth-rinse index

To investigate dental erosion in employees working with sulfuric acid at a lead storage battery manufacturing plant and level of personal exposure to sulfuric ions, we measured sulfuric ion concentrations in the mouth rinse of those employees. We also measured exposure levels from air samples obtained from 2 employees from the same plant who did not work with sulfuric acid using a portable air sampler. At the same time, we collected and compared their mouth rinses with those from other employees. More specifically, we measured and compared sulfuric ion, calcium, and magnesium concentrations, along with pH levels from the mouth rinse of these two groups. Positive correlations were found between sulfuric ion and calcium concentrations (r=0.61, p<0.005), calcium and magnesium concentrations (r=0.61, p<0.005), Ca/Mg and calcium concentrations (r=0.64, p<0.005), and sulfuric ion and magnesium concentrations (r=0.55, p<0.005). Negative correlations were found between sulfuric ion concentrations and pH levels (r=-0.31, p<0.01), and magnesium concentrations and pH levels (r=-0.32, p<0.01). This suggests that mouth rinse from employees working with sulfuric acid could function as an indicator of sulfuric ion concentration in the work environment. Furthermore, this could lead to the development of a more accurate indicator of individual exposure.

Occupational exposure to acidic chemicals and occupational dental erosion

OBJECTIVE

This study investigated the association between occupational acidic chemicals (ACs) exposure and occupational dental erosion.

METHODS

A cross-sectional study was conducted in which three dentists surveyed 951 subjects from 42 factories using five types of ACs below Korean Threshold Limit Values (K-TLVs). Subjects agreed to participate by a written consent; 519 were acid exposed workers and 431 were non-exposed. The modified ten Bruggen Cate's criteria was used to classify erosion. Length and type of exposure to ACs were assessed using questionnaires. Logistic regression analysis including interaction terms was applied.

RESULTS

ACs exposure was associated with erosion severity. Multiple exposures to ACs were found to be strongly associated with severe erosion. Interaction between wearing masks and AC exposure was significant.

CONCLUSIONS

This study showed a clear association between AC exposure below K-TLVs and erosion. Hence, the authors propose to lower K-TLVs of five types of ACs.

Associations Between Occupational Health Behaviors and Occupational Dental Erosion

OBJECTIVES

The aim of this study was to evaluate the associations between occupational health behaviors and occupational dental erosion.

METHODS

Using data for 943 workers among 34 factories, selected by three-stage stratified cluster sampling from 888 factories using acids, two sets of modified case-control studies were performed. The cases were 242 workers with any dental erosion (G1-5) and 78 with severe dental erosion (G3-5); the controls were 701 workers with no erosion (GO) and 864 workers with no or mild erosion grades, GO-2, respectively. The main explanatory variables were behaviors such as wearing a respiratory mask and gargling at work. The results were adjusted for employment, age, sex, knowledge, and opinion about occupational health, attrition, and abrasion. Bivariate and multivariate logistic regression analyses were conducted.

RESULTS

The odds of overall occupational dental erosion (G1-5) was 0.63 (95% CI = 0.42, 0.94) for respiratory mask wearers compared to nonwearers; the odds of severe occupational dental erosion (G3-5) was not significantly less in respiratory mask wearers (OR = 0.94; 95% CI = 0.53, 1.67). Gargling did not show a significant association with occupational dental erosion in this study.

CONCLUSIONS

Among occupational health behaviors, wearing personal protective respiratory masks in work was significantly associated with less overall occupational dental erosion.

Clinical and histopathological changes of the nasal mucosa induced by occupational exposure to sulphuric acid mists

AIMS

To assess potential alterations of the nasal mucosa by clinical and histopathological evaluation of workers exposed to sulphuric acid mists at anodising plants, correlating the findings with duration of exposure and sulphuric acid concentrations in the air, and comparing them with a control group.

METHODS

Fifty two workers from five plants underwent a clinical evaluation (standard questionnaire, clinical, and ear, nose, and throat examination including nasal endoscopy). For the histopathological study, 20 of the 52 subjects (study group) were randomly selected, as well as 11 unexposed subjects (control group), matched by sex, age, and smoking habits. Nasal biopsy specimens were obtained from the anterior septum mucosa and the anterior curvature of the middle turbinate in each individual. A total of 56 nasal mucosa specimens (37 in the study group and 19 in the control group) were evaluated with regard to normal respiratory epithelium or metaplastic epithelium, atypia or dysplasia, and alterations of the lamina propria.

RESULTS

The histopathological study revealed squamous metaplasia in 29 (79%) and atypia in 13 (35%) of the 37 study group samples. No association was found between exposure duration and the clinical and histopathological variables, but a significant association was found between sulphuric acid concentrations higher than 200 micro g/m(3) and pale mucosal patches and ulcerations in the exposed subjects. Logistic regression analysis showed that the exposed subjects had a fivefold risk of developing atypia compared with the unexposed subjects.

CONCLUSIONS

Workers exposed to sulphuric acid mists presented with a high incidence of nasal symptoms, and macroscopic and microscopic changes of the nasal mucosa, including squamous atypia and dysplasia. The risk for these histopthological lesions increased with higher sulphuric acid concentrations in the air, revealing an exposure-response relation.

Associated postmortem dental findings as an aid to personal identification

The use of the unique features of the human dentition to aid in personal identification is well accepted within the forensic field. Indeed, despite advances in DNA and other identification methodologies, comparative dental identifications still play a major role in identifying the victims of violence, disaster or other misfortune. The classic comparative dental identification employs the use of postmortem and antemortem dental records (principally written notes and radiographs) to determine similarities and exclude discrepancies. In many cases the tentative identification of the individual is unknown and therefore antemortem records cannot be located. In such a situation a dental profile of the individual is developed to aid the search for the individual's identity. With such a profile a forensic odontologist can identify and report indicators for age at time of death, race (within the four major ethnic groups) and sex. In addition to these parameters the forensic dentist may be able to give more insight into the individual. This paper outlines, for the non-expert, some of the additional personal information that can be derived from the teeth of the deceased, and which may assist in their ultimate identification.

Upper aerodigestive cancer in battery manufacturers and steel workers exposed to mineral acid mists

OBJECTIVE

To assess the risk of cancer from inhalation of mineral acid mists.

METHODS

A cohort study and nested case-control study of upper aerodigestive tumours were carried out in men employed since 1950 at two battery plants and two steel works in Britain. The cohort was identified from personnel records and included 2678 men with definite exposure to acid mists (mainly sulphuric acid), 367 with possible exposure, and 1356 who were unexposed. Mortality was compared with that in the national population by the person-years method. Cases of upper aerodigestive cancer were identified from death certificates and cancer registrations, and their exposure to acids was compared with that of age matched controls (five per case) from the same plant by conditional logistic regression.

RESULTS

In follow up to 31 December 1993, 93% of men were traced, including 1277 who had died. Among the men definitely exposed to acid mists, overall mortality was less than in the national population (standardised mortality ratio (SMR) 0.92, 95% confidence interval (95% CI) 0.85-0.98) as was mortality from all cancers (SMR 0.92, 95% CI 0.79-1.05) and specifically from cancer of the larynx (SMR 0.48, 95% CI 0.01-2.70) and lung (SMR 0.98, 95% CI 0.78-1.22). A total of 15 incident or fatal cases of upper aerodigestive cancer were identified during follow up. When these men were compared with controls, risk was moderately increased in those who had worked for at least five years in jobs entailing exposures to sulphuric or hydrochloric acid in excess of 1 mg/m3 (OR 2.0, 95% CI 0.4-10).

CONCLUSIONS

These findings are consistent with those from other studies which have indicated a hazard of upper aerodigestive cancer from acid mists. However, they indicate that any risk from exposures to sulphuric and hydrochloric acid below 1 mg/m3 is small.

Epidemiological-environmental study of lead acid battery workers. II. Acute effects of sulfuric acid on the respiratory system

Two hundred and twenty-five (225) workers in five lead acid battery plants were administered a questionnaire containing work-related symptoms, underwent spirometry, and had personal samples for H2SO4 taken over the shift. Most personal samples were less than 1 mg/m3 H2SO4. Mass median aerodynamic diameter of H2SO4 from area samples in the formation areas was 2.6-10 micron. Workers with a higher exposure to acid did not have an increased rate of acute work-related symptoms. Changes in pulmonary function over the shift were not related to levels of airborne lead or airborne acid, sex, age, or smoking status. In acclimated workers, there is no evidence of acute symptoms or reductions in pulmonary function over the shift at concentrations less than 1 mg/m3.