Self-recording audiometry in industry

Pelmear, P. L. and Hughes, Brenda J. (1974).British Journal of Industrial Medicine,31, 304-309. Self-recording audiometry in industry. A study of initial and repeat audiograms of 118 drop forge employees using fixed frequency self-recording audiometry showed that the mean of the differences at the test frequencies 0·5, 1, 2, 3, 4, and 6 kHz ranges from -0·47 dB to +0·61 dB. The largest standard deviation was 6 dB at 6 kHz and the lowest 3 dB at 2 kHz.

The results also confirmed that temporary threshold shift effects may be minimized if audiograms are obtained at the beginning of a shift or within two hours provided the subject is protected with ear muff defenders up to the time of the test.

The practical advantages to industry of using self-recording audiometry for audiometric screening and the reliability of single audiograms for threshold determination are discussed.

     

噪声习服对听力损伤保护作用的时程研究

目的观察噪声习服对豚鼠听力损伤防护效应的时程变化。方法20只雄性豚鼠随机分为噪声习服组（A组）和直接暴露组（B组）。A组动物在声压级为90 dB SPL（声压级）、中心频率为0.5 kHz的一个倍频程噪声下连续暴露10 d,每天6 h,休息5 d,然后与B组动物同时在105 dB的白噪声下连续暴露7 d,每天4 h。每天在强噪声暴露前、后测定两组动物的听觉脑干反应（ABRs）阈值。结果A组动物在接受低噪声暴露后产生了习服效应。强噪声暴露后,A组1-7 d的平均阈移逐渐增加,而B组的平均阈移则逐渐减少;除第7天时的6 kHz频率外,A组在各时点上的click和短纯音（4、6、8 kHz）的平均阈移均显著低于B组。结论噪声习服对强噪声暴露引起的听力损伤具有一定的保护作用,但随着时间的推移,这种作用逐渐减弱。     

Studies of combined effects of sinusoidal whole body vibrations and noise of varying bandwidths and intensities on TTS2 in men

Summary This study analyses the data from three laboratory experiments concerning the separate and combined effects on temporary threshold shifts in hearing (TTS2) of sinusoidal low-frequency (5 Hz — 2.12 m/s² and 10 Hz —2.65 m/s²), whole body vibration (along the Z-axis), and continuous (white) noise with eight different bandwidths and intensity levels of 85 dB(A), 90 dB(A) and 98 dB(A). Altogether 370 separate personal experiments were performed using a one-man exposure chamber system. A single experiment consisted of a 30-min pre-exposure period, three 16-min exposure periods, and a 15-min post-exposure period. The data suggested that the TTS₂ induced by noise was increased by vibration. Actually, vibration at a frequency of 5 Hz and noise with bandwidths of 1–4 kHz, 1–8 kHz or 0.2–16 kHz comprised the most significant exposure combinations. After such exposures, the increase in TTS₂ values was defined most clearly for 4 kHz and 6 kHz test frequencies. The increase of thresholds was most marked during the first 16-min exposure period, even though most TTS₂ values determined after the third consecutive exposure period were higher than after the first and second exposures. Figures obtained after the third exposure period proved that exposure to simultaneous vibration and broad band noise (i.e. noise with a bandwidth of 0.2–16 kHz) increased TTS₂ values 1.2–1.5 times more in the 4 kHz audio range than such a broad band noise alone. No single vibration condition induced the same amount of TTS₂.     

The Nord-Trøndelag Norway Audiometric Survey 1996-98: unscreened thresholds and prevalence of hearing impairment for adults > 20 years

As supplement to a general health screening examination (HUNT-II), we conducted a puretone audiometry study in 1996-98 on adults (>20 years) in 17 of 23 municipalities in Nord-Tr?ndelag, Norway, including questionnaires on occupational and leisure noise exposure, medical history, and symptoms of hearing impairment. The study aims to contribute to updated normative hearing thresholds for age and gender, while evaluating the effects of noise exposure, medical history, and familial or genetic influences on hearing. This paper presents the unscreened hearing threshold data and prevalence of hearing impairment for different age groups and by gender. Valid audiometric data were collected from 62% (n=50,723) of 82,141 unscreened invited subjects (age-range 20-101 years, mean=50.2 years, SD=17.0 years). Two ambulant audiometric teams each conducted 5 parallel self-administered, pure-tone hearing threshold examinations with the standard test frequencies 0.25-0.5-1-2-3-4-6-8 kHz (manual procedure when needed). Tracking audiometers were used in dismountable booths with in-booth noise levels well within ISO criteria, except being at the criterion around 200 Hz. The data were electronically transferred to a personal computer. Test-retest correlations for 99 randomly drawn subjects examined twice were high. The mean thresholds recorded were some dB elevated from "audiometric zero" even for age group 20-24 years. As also found in other studies, this might indicate too restrictive audiometric reference thresholds. Males had slightly better hearing < or =0.5 kHz for all age groups. Mean thresholds were poorer in males > or = 30 years from > or =2 kHz, with maximal gender differences of approximately 20 dB at 3-4 kHz for subjects aged 55-74 years. Weighted prevalence data averaged over 0.5-1-2-4 kHz showed hearing impairment >25 dB hearing threshold level of 18.8% (better ear) and 27.2% (worse ear) for the total population--for males 22.2% and 32.0%, for females 15.9% and 23.0%, respectively. Mean hearing loss > or =10 dB at 6 kHz registered for both genders even in age groups 20-24 years may be partly due to calibration artefacts, but might possibly also reflect noise-related socio-acusis.     

The Reliability of Repeated Auditory Threshold Determination

This paper considers the precision which may be expected in short-term serial measurements of audiometric thresholds.

Twelve otologically normal young men were tested on four separate occasions at 1, 2, 3, 4, 6, 8, 0·5, and 1 kc/s. The tests were carried out in a mobile test room installed in a specially constructed vehicle chassis.

The acoustic output of the audiometer and ear-phones was measured at intervals throughout the investigation. Output stability with variations of mains supply voltage and drift during the warming-up period of the instrument were also measured.

It was concluded that the instrument variation had been extremely slight throughout the investigation.

The estimates of variance of repeated threshold determinations on a single ear were found to be 8·5 (dB)² at 0·5 kc/s, 6 (dB)² at 3 kc/s, and 23 (dB)² at 8 kc/s. Differences between consecutive determinations extended to 25 dB.

These results were obtained under conditions which practically precluded all sources of variation other than that due to the inherent uncertainty of audiometric measurements. It appears to follow, therefore, that if an apparent drop in auditory threshold in one ear is to be considered as significant evidence (P = 1%) of a real change, the difference would have to be at least 17·5 dB at the higher frequencies. This level could possibly be reduced to 10 dB if the change occurred simultaneously at both 4 and 6 kc/s.

     

Circadian variation of F.E.V. in shift workers

Guberan, E., Williams, M. K., Walford, Joan, and Smith, Margaret M. (1969).Brit. J. industr. Med.,26, 121-125. Circadian variation of F.E.V. in shift workers. The one-second forced expiratory volume (F.E.V._1·0), the forced vital capacity, and the oral temperature were measured in a group of men working a rotating three-shift system—2 to 10 p.m. one week, 10 p.m. to 6 a.m. the next week, and 6 a.m. to 2 p.m. the third week. The outside air temperature at the London Weather Centre was also obtained. Measurements were made on Mondays and Fridays at the beginning, middle, and end of the shift.

The mean F.E.V._1·0 of 19 normal men showed an increase of 0·15 litre (4·1%) between the beginning and end of both the morning shifts, a mean decrease of some 0·05 litre (1·5%) between the beginning and end of the afternoon shifts, and little change during the night shifts. This circadian variation could not be attributed to industrial fume, smoking or a learning effect.

The findings will be of practical importance when F.E.V. is measured in shift workers to determine the effects of toxic substances on ventilatory capacity.

     

Blood lead and the symptoms of lead absorption

ABSTRACT Eighty-one percent of all hourly paid men who had been employed for more than six months in a factory making lead acid batteries and plastics completed a modified Cornell medical index health questionnaire. Blood lead and erythrocyte protoporphyrin (EPP) were also measured. The questions were grouped into symptom categories as follows: all physical, all psychological, “potentially lead induced,” pulmonary, cardiovascular, gastrointestinal, skin, nervous system, genitourinary, and fatigue. For each symptom category the pooled percentages of men whose symptom scores were above the common median of the three blood lead groups 10-, 40-, and 60 and over μg/100 ml (0·48-, 1·93-, and 2·90 and over μmol/l) within age/smoking subgroups were calculated. In every symptom category the percentages in the two lower blood lead groups differed little, but the percentages were consistently higher in men with blood concentration of 60 μg/100 ml (2·90 μmol/l) and over. Differences between a combined 10-59 μg/100 ml (0·48-2·85 μmol/l) blood lead group and the 60 and over μg/100 ml (≥2·90 μmol/l) group were statistically significant at the 0·01 level for “potentially lead induced” symptoms and at the 0·05 level for skin and psychological symptoms. Broadly similar results were obtained with four log₁₀ EPP groups 0·6-, 1·5-, 1·7-, and ≥2·0, but differences did not reach statistical significance. There was no obvious explanation as to why symptoms that are not found in classic lead poisoning should be increased almost as much as those that are. It was thought that these results could be biased due to the men's knowledge of the symptoms associated with lead exposure, but the possibility that they may be partly due to lead absorption cannot be excluded.     

Erythrocyte arginase activity as an indicator of lead exposure

ABSTRACT A semi-automated method has been developed for the determination of the arginase activity of erythrocytes using dried blood spots, which are easy to prepare on site in a factory for later laboratory analysis. The mean arginase activity of erythrocytes in 49 men occupationally exposed to lead was 62·9 IU/g·Hb (SD, 14·4 IU/g·Hb); in 45 men not exposed to lead the mean was 44·6 IU/g·Hb (SD, 11·6 IU/g·Hb). A significantly higher mean arginase activity was found in the specimens from lead-exposed workers (p < 0·001). The correlation coefficient between blood lead and erythrocyte arginase was r = 0·67 (p < 0·001). The degree of correlation between blood lead and lead indicators including arginase was r = 0·75 for urine δ-aminolaevulinic acid, r = 0·67 for erythrocyte arginase, r = 0·66 for urine lead, and r = 0·63 for coproporphyrin. Erythrocyte arginase showed no significant correlation in the liver function tests, GOT, GPT, and albumin in serum. When 40 μg/100 g of blood lead concentration was fixed as the basic value and 56·2 IU/g·Hb of erythrocyte arginase activity was set as the screening value in lead-exposed workers, the sensitivity and specificity of the arginase test were 0·96 and 0·65, respectively. Thus the validity of the test was calculated to be 1·61. These results show that the arginase level of erythrocytes can be considered to be one of the significant indicators of occupational exposure to lead because it reflects well the dose-response relationship of lead in the human body. Our method allows rapid analysis of erythrocyte arginase and thus should be useful in screening for lead exposure.     

Hearing loss in workers exposed to toluene and noise

In this study we investigated the risk of hearing loss among workers exposed to both toluene and noise. We recruited 58 workers at an adhesive materials manufacturing plant who were exposured to both toluene and noise [78.6-87.1 A-weighted decibels; dB(A)], 58 workers exposed to noise only [83.5-90.1 dB(A)], and 58 administrative clerks [67.9-72.6 dB(A)] at the same company. We interviewed participants to obtain sociodemographic and employment information and performed physical examinations, including pure-tone audiometry tests between 0.5 and 6 kHz. A contracted laboratory certified by the Council of Labor in Taiwan conducted on-site toluene and noise exposure measurements. The prevalence of hearing loss of >or=25 dB in the toluene plus noise group (86.2%) was much greater than that in the noise-only group (44.8%) and the administrative clerks (5.0%) (p<0.001). The prevalence rates were 67.2, 32.8, and 8.3% (p<0.001), respectively, when 0.5 kHz was excluded from the estimation. Multivariate logistic regression analysis showed that the toluene plus noise group had an estimated risk for hearing loss>or=25 dB, 10.9 times higher than that of the noise-only group. The risk ratio dropped to 5.8 when 0.5 kHz was excluded from the risk estimation. Hearing impairment was greater for the pure-tone frequency of 1 kHz than for that of 2 kHz. However, the mean hearing threshold was the poorest for 6 kHz, and the least effect was observed for 2 kHz. Our results suggest that toluene exacerbates hearing loss in a noisy environment, with the main impact on the lower frequencies.     

Prevalence of noise-induced hearing loss among woodworkers in Nepal: a pilot study

Background: The woodworking industry represents an important cause of occupational noise-induced hearing loss (NIHL), a significant yet underappreciated problem in many developing countries.Objectives: To describe the prevalence of occupational NIHL among woodworkers in Nepal and measure noise levels at workplaces.Methods: We conducted a cross-sectional study with 124 woodworkers (88 carpenters, 36 sawyers), recruited through convenience sampling from 26 workplaces. Pure-tone audiometry between the frequencies 0·5 and 8 kHz ascertained participants’ hearing status, and noise readings were taken at selected workplaces.Results: In all, 31% of carpenters and 44% of sawyers met criteria for NIHL, with 7 and 17% meeting World Health Organization (WHO) criteria for hearing impairment (HI), respectively. Noise levels at various workplaces ranged from 71·2 to 93·9 dBA.Conclusions: Woodworkers in Nepal are at risk of occupational NIHL. As the industry develops, this problem will likely become more extensive, highlighting the need for workplace interventions and additional research.     

Peak flow rate in relation to forced expiratory volume in hemp workers

Žuškin, E., and Valić, F. (1971).Brit. J. industr. Med.,28, 159-163. Peak flow rate in relation to forced expiratory volume in hemp workers. Measurements of the forced expiratory volume in one second (FEV_1·0) and the peak expiratory flow rate (PEF) were made in 99 non-smoking female hemp workers before and after the shift. A significant mean reduction of both FEV_1·0 and PEF (P<0·01) over the shift was found in workers both with and without byssinosis but the relative reductions of PEF were more pronounced (FEV_1·0 15·3%; PEF 20·8%). There was a significant positive correlation (P<0·01) both between absolute FEV_1·0 and PEF values measured before work (with byssinosis r = 0·605; without byssinosis r = 0·461), and between FEV_1·0 and PEF changes over the shift (with byssinosis r = 0·725; without byssinosis r = 0·631). There was also a significant correlation between FEV_1·0 and PEF changes following Alupent inhalation after the shift with more pronounced effects on PEF. The coefficients of variation in FEV_1·0 and PEF measurements (by the Bernstein type spirometer and the Wright peak flow meter) proved approximately equal.     

Campylobacter jejuni and salmonella in raw red meats: A Public Health Laboratory Service Survey*

Thirty-one laboratories examined a total of 6169 meat samples, 1236 from abattoirs and 4933 from retail and other outlets. Campylobacter jejuni was isolated from 98 (1·6%). A higher isolation rate of 49/1236 (4·0%) was found among abattoir than among retail and other samples (49/4933-1·0%). Twenty-two of the laboratories looked for salmonella; although 94/4002 (2·3%) were positive, in only one sample of minced beef were campylobacter and salmonella found together. Isolation rates for salmonellae were 75/3576 (2·1%) from retail and 19/426 (4·5%) from abattoir samples.     

Monday Morning Auditory Threshold in Weavers

The view is questioned that 5.00 p.m. on Friday to 8.00 a.m. on Monday constitutes an adequate interval for the recovery of occupationally induced temporary threshold shift.

Group mean pure tone thresholds were determined for a group of young weaving shed operatives on a Monday morning and compared with those obtained, from the same group, after a 16-day absence from noise.

The 16-day thresholds were lower than the results on a Monday morning; the largest mean difference was at 4 kc/s and amounted to 7·3 dB.

It was concluded that the Monday morning threshold of these weavers had a component of temporary threshold shift, the exact magnitude of which is unknown.

     

Dynamics of high-frequency hearing loss of operators of industrial ultrasonic devices

Summary This investigation was aimed at elucidating the dynamics of hearing loss in the range of 500 Hz to 20kHz of 26 Ultrasonic (Uls)-operators exposed to high-frequency noise exceeding known hygienic limits. Results of audiometric tests performed twice, before and after a period of three years, were compared. The determined hearing-threshold-shift in the range of 500Hz to 13 kHz could be explained as the effect of aging, whereas in the range of 13 to 17 kHz the stated mean threshold elevation of 2–5 dB, beyond the hearing loss connected with aging within three years, is the consequence of high-frequency noise exposure. On this basis the dynamics of high-frequency hearing loss of 1 dB/year in the case of continued exposure to high-frequency noise could be calculated. Apart from the observed threshold elevation, the fraction of ears responding to acoustic stimuli at the highest frequencies decreases by about 10% with frequency increase of 1 kHz in the range of 13 to 19 kHz. This indicates that the hearing organ is more susceptible to high-frequency noise at the highest hearing frequencies.     

Asbestos-related occupational cancers compensated under the Spanish National Insurance System, 1978–2011

Background:

In 1978, asbestos-related occupational cancers were added to the Spanish list of occupational diseases. However, there are no full accounts of compensated cases since their inclusion.

Objective:

To analyze the cases of asbestos-related cancer recognized as occupational in Spain between 1978 and 2011.

Methods:

Cases were obtained from the Spanish Employment Ministry. Specific incidence rates by year, economic activity, and occupation were obtained. We compared mortality rates of mesothelioma and bronchus and lung cancer mortality in Spain and the European Union.

Results:

Between 1978 and 2011, 164 asbestos-related occupational cancers were recognized in Spain, with a mean annual rate of 0·08 per 10⁵ employees (0·13 in males, 0·002 in females). Under-recognition rates were an estimated 93·6% (males) and 99·7% (females) for pleural mesothelioma and 98·8% (males) and 100% (females) for bronchus and lung cancer. In Europe for the year 2000, asbestos-related occupational cancer rates ranged from 0·04 per 10⁵ employees in Spain to 7·32 per 10⁵ employees in Norway.

Conclusions:

These findings provide evidence of gross under-recognition of asbestos-related occupational cancers in Spain. Future work should investigate cases treated in the National Healthcare System to better establish the impact of asbestos on health in Spain.     

Excretion kinetics of urinary metabolites in a patient addicted to trichloroethylene

Ikeda, M., Ohtsuji, H., Kawai, H., and Kuniyoshi, M. (1971).Brit. J. industr. Med.,28, 203-206. Excretion kinetics of urinary metabolites in a patient addicted to trichlorethylene. A male Japanese subject, single, aged 38, who worked at a workshop washing metal parts with trichloroethylene, was admitted to our clinic due to addiction to the solvent. Analyses of urine revealed the presence of up to 160 μg/ml of trichloro-compounds (mostly trichloroacetic acid) which gradually disappeared in three weeks as the psychotic symptoms cleared up. The excretion half-lives of trichloroethylene metabolites for the initial rapid phase (succeeding slow phase in parentheses) were 5·8 (49·7) hours for trichloroethanol, 22·5 (72·6) hours for trichloroacetic acid, and 7·5 (72·6) hours for total trichloro-compounds.     

Noise exposure and cognitive performance: A study on personnel on board Royal Norwegian Navy vessels

Prior research shows that work on board vessels of the Royal Norwegian Navy (RNoN) is associated with noise exposure levels above recommended standards. Further, noise exposure has been found to impair cognitive performance in environmental, occupational, and experimental settings, although prior research in naval and maritime settings is sparse. The aim of this study was to evaluate cognitive performance after exposure to noise among personnel working on board vessels in the RNoN. Altogether 87 Navy personnel (80 men, 7 women; 31 ± 9 years) from 24 RNoN vessels were included. Noise exposure was recorded by personal noise dosimeters at a minimum of 4 h prior to testing, and categorized into 4 groups for the analysis: <72.6 dB(A), 72.6-77.0 dB(A), 77.1-85.2 dB(A), and >85.2 dB(A). The participants performed a visual attention test based on the Posner cue-target paradigm. Multivariable general linear model (GLM) analyses were performed to analyze whether noise exposure was associated with response time (RT) when adjusting for the covariates age, alertness, workload, noise exposure in test location, sleep the night before testing, use of hearing protection device (HPD), and percentage of errors. When adjusting for covariates, RT was significantly increased among personnel exposed to >85.2 dB(A) and 77.1-85.2 dB(A) compared to personnel exposed to <72.6 dB(A).     

维生素E对短期噪声暴露引起豚鼠听力损失的预防作用

目的研究维生素E对噪声性听力损失是否具有预防作用。方法48只雄性花色豚鼠随机分为6组,每组8只。1、2、3、4组进行中心频率为4kHz、强度为100dB(A)的倍频程噪声暴露,8h/d,连续3d;于噪声暴露前3d、噪声暴露的每一天及噪声暴露后3d,分别腹腔注射生理盐水、玉米油、10.0mg/kg维生素E、50.0mg/kg维生素E,1次/d,连续9d;5、6组不接受噪声暴露,分别腹腔注射生理盐水、50.0mg/kg的维生素E,注射时间同噪声暴露组。比较噪声暴露后即刻及2、8d,各组豚鼠听觉脑干反应(ABR)阈移,评价维生素E对噪声性听力损失的预防作用。结果第3组豚鼠在噪声暴露后即刻及2、8d,在2、4、8kHz处的ABR阈移分别为(15.9±6.8)、(39.4±4.8)、(42.5±6.3)、(0.3±2.5)、(19.1±7.9)、(21.9±6.4)、(0.3±1.6)、(10.9±8.6)、(12.2±8.1)dB,明显低于第1组豚鼠在噪声暴露后即刻及2、8d,在2、4、8kHz处的ABR阈移[分别为(30.9±11.3)、(47.8±8.8)、(49.7±6.9)、(10.0±3.5)、(29.1±6.5)、(29.1±7.6)、(4.7±3.6)、(20.3±6.5)、(17.5±9.0)dB],差异有统计学意义(P<0.05)。第4组豚鼠在噪声暴露后即刻及2、8d,在2、4、8kHz处的ABR阈移分别为(14.4±5.3)、(36.6±4.4)、(43.1±2.9)、(0.3±2.5)、(16.9±4.6)、(19.4±3.2)、(0.0±3.7)、(7.5±4.2)、(9.1±4.2)dB,明显低于第1组豚鼠在噪声暴露后即刻及2、8d,在2、4、8kHz处的ABR阈移,差异亦有统计学意义(P<0.05)。结论维生素E具有一定的预防噪声性听力损失的作用。     

A neurological and biochemical study of early lead poisoning

ABSTRACT Changes in nerve conduction velocity were found in 94 workers exposed to lead in a battery factory compared with 94 age-matched controls. There was no clinical evidence of nerve damage in the lead workers. The mean blood lead concentration in the 94 lead workers was 2·9 μmol/l (60 μg/100 ml) and their length of exposure to lead ranged from 6 months to 33 years.

All mean maximum motor nerve conduction velocities (MMCV) measured were highly statistically significantly lower in the lead-exposed group when compared with their age-matched controls. Thus mean ulnar MMCV was 53·4 m/s in lead workers and 55·6 m/s in control subjects (p < 0·0005); mean median MMCV was 55·9 m/s in lead workers and 57·3 m/s in control subjects (p < 0·01); mean radial MMCV was 63·9 m/s in lead workers and 71·1 m/s in control subjects (p < 0·0005); mean peroneal MMCV was 46·1 m/s in lead workers and 47·6 m/s in control subjects (p < 0·005).

The amplitude of the muscle action potential produced by proximal stimulation of a nerve was expressed as a percentage of the amplitude of the muscle action potential produced by distal stimulation and the percentage amplitude thus obtained used as an indicator of the conduction velocity of slower fibres (SFCV). Peroneal nerve percentage amplitude of lead workers was statistically significantly lower (p < 0·005) than in the control group (means 86·6% and 90·3% respectively). There were, however, no significant differences in the percentage amplitude in the ulnar and median nerves. It is suggested that percentage amplitude is an inappropriate indicator of SFCV in ulnar and median nerves.

There was no statistically significant correlation to indicate that progressive slowing of nerve conduction (MMCV and SFCV) was associated with increasing exposure to lead (as indicated by blood and urine lead concentrations) or with the commonly measured biochemical changes associated with disturbed haemopoiesis in lead exposure (δ-aminolaevulinic acid dehydrase; free erythrocytc protoporphyrin; haemoglobin and urinary δ-aminolaevulinic acid). MMCV of the ulnar nerve was the only conduction velocity statistically significantly correlated with length of exposure to lead. Increased length of exposure to lead was associated with a decrease in the ulnar MMCV.

Only 13 of the subjects had been exposed to lead for two years or less and in none of them had the blood lead ever risen above 3·9 μmol/l (80 μg/100 ml) in three-monthly tests (mean blood lead concentration at time of testing: 2·8 μmol/l). In these subjects the MMCV of ulnar, radial, and peroneal nerves and the peroneal percentage amplitude were statistically significantly reduced. The results from this group suggest that the onset of nerve conduction changes occurs within two years and at concentrations of lead in blood of less than 3·9 μmol/l (80 μg/100 ml).

     

Determination of blood lead using a 4·0 mm paper punched disc carbon sampling cup technique

Cernik, A. A. (1974).British Journal of Industrial Medicine,31, 239-244. Determination of blood lead using a 4·0 mm paper punched disc carbon sampling cup technique. The method described is designed to overcome difficulties associated with presentation of the sample and its analysis for lead in blood. Chromium-51 studies on the effect of spread showed that imprecision resulted when discs of less than 4·0 mm diameter were punched from a given blood spot. The best standard deviation and relative standard deviation for increasing lead concentrations was obtained when 4·0 mm discs were used.

Small daily voltage variations to the carbon cup workhead required that the non-specific absorption should be controlled to 0·02 absorbance at the ashing step. The occurrence of a second non-atomic signal was not considered significant since it had a different volatilization temperature to lead.

Several advantages of the method are stated.

A comparison of 4·0 mm against 6·5 mm punched discs was investigated using 33 samples of blood ranging from 9·0 to 126 μg of lead per 100 ml blood. Correlation (r = 0·970) and regression lines are shown. Absolute sensitivity of the method was 25 × 10^-12 g.