A cohort study of workers exposed to formaldehyde in the British chemical industry: an update

A cohort study of workers exposed to formaldehyde in the British chemical industry in any one of six factories has been extended after the earlier published report in 1984. A further eight years of follow up to the end of 1989 have been included for the originally reported 7660 workers first employed before 1965, and a first follow up to the same date has been carried out for 6357 workers first employed since 1964. Extensive checking of the database has taken place including records at the factories, the MRC Environmental Epidemiology Unit, and the National Health Service Central Register. The updated findings include one death from nasal cancer compared with 1.7 expected in this number of men during the follow up period--which gives no support to the original hypothesis based on animal experimental data that formaldehyde may be a nasal carcinogen in humans. There have been no cases of nasopharyngeal cancer in the cohort compared with an estimated 1.3 expected--which gives no support to the findings in a similarly designed study in the United States of an excess of cancers of the nasopharynx associated with exposure to formaldehyde. There has been a slight excess of about 12% for lung cancer with 402 deaths compared with about 359 expected. This is similar to that found in the United States study, but higher than we reported earlier before the checking procedures and extended follow up. Further analysis gives no definitive indication of this excess of lung cancer being clearly related to formaldehyde exposure, and the increase is within that generally thought consistent with possible confounding effects of cigarette smoking (although no data are available on this point).

Thinness at birth in a northern industrial town

OBJECTIVE

To determine whether babies in an area of Britain with unusually high perinatal mortality have different patterns of fetal growth to those born elsewhere in the country.

DESIGN

Measurement of body size in newborn babies.

SETTING

Burnley (perinatal mortality in 1988 15.9/1000 total births) and Salisbury (perinatal mortality 10.8/1000 total births), England.

SUBJECTS

Subjects comprised 1544 babies born in Burnley, Pendle, and Rossendale Health District, and 1025 babies born in Salisbury Health District.

MAIN OUTCOME MEASURES

Birthweight, length, head, arm and abdominal circumferences, and placental weight were determined.

RESULTS

Compared with babies born in Salisbury, Burnley babies had lower mean birthweight (difference 116 g, 95% confidence interval (CI) 77,154), smaller head circumferences (difference 0.3 cm, 95% CI 0.2, 0.4), and were thinner as measured by arm circumference (difference 0.3 cm, 95% CI 0.3, 0.4), abdominal circumference (difference 0.5 cm, 95% CI 0.4, 0.6) and ponderal index (difference 0.8 kg/m3, 95% CI 0.6, 1.0). The ratio of placental weight to birthweight was higher in Burnley (difference 0.6%, 95% CI 0.4, 0.9). These differences were found in boys and girls and did not depend on differences in duration of gestation or on the different ethnic mix of the two districts. Mothers in Burnley were younger, shorter in stature, had had more children, were of lower social class, and more of them smoked during pregnancy than mothers in Salisbury. These differences did not explain the greater thinness of their babies.

CONCLUSIONS

Babies born in Burnley, an area with high perinatal mortality, are thin. The reason is unknown. Poor maternal nutrition is suspected because Burnley babies have a higher ratio of placental weight to birthweight. The greater thinness at birth of Burnley babies could have long term consequences, including higher rates of cardiovascular disease.

Sunlight exposure, antioxidant status, and cataract in Hong Kong fishermen

STUDY OBJECTIVES

The aim was to test whether cataract is associated with higher lifetime exposure to sunlight, and whether antioxidants protect against cataract.

DESIGN

This was a cross sectional survey of eye disease, with assessment of antioxidant status in a subgroup.

SETTING

Hong Kong fishing communities in 1989.

PARTICIPANTS

685 men and women aged 55 to 74 years old were included in the study, of whom 367 (54%) attended hospital for detailed examination.

MEASUREMENTS AND MAIN RESULTS

At a mobile clinic visual acuity and lens opacities were assessed, and using a questionnaire, occupational history and lifetime exposure to sunlight. At hospital ophthalmic measurements were repeated and blood was taken for measurement of plasma vitamin C, vitamin E, and total carotenoids, and red cell activities of glucose-6-phosphate dehydrogenase, glutathione peroxidase, superoxide dismutase, and catalase. Higher grades of cataract (particularly nuclear cataract) tended to be more common in subjects with the most sun exposure, although not to the point of statistical significance. In contrast to earlier studies, no association was found with antioxidant status.

CONCLUSIONS

The findings give some support to the hypothesis that sunlight causes cataract. The absence of a relation to antioxidant status may be because blood levels of antioxidants at one point in time do not adequately reflect a subject's past metabolic state, and particularly the past activity of antioxidants in the lens.

Initiation of hypertension in utero and its amplification throughout life

OBJECTIVE

To determine whether the relation between high blood pressure and low birth weight is initiated in utero or during infancy, and whether it changes with age.

DESIGN

A longitudinal study of children and three follow up studies of adults.

SETTING

Farnborough, Preston, and Hertfordshire, England, and a national sample in Britain.

SUBJECTS

1895 children aged 0-10 years, 3240 men and women aged 36 years, 459 men and women aged 46-54 years, and 1231 men and women aged 59-71 years. The birth weight of all subjects had been recorded.

MAIN OUTCOME MEASURE

Systolic blood pressure.

RESULTS

At all ages beyond infancy people who had lower birth weight had higher systolic blood pressure. Systolic blood pressure was not related to growth during infancy independently of birth weight. The relation between systolic pressure and birth weight became larger with increasing age so that, after current body mass was allowed for, systolic pressure at ages 64-71 years decreased by 5.2 mm Hg (95% confidence interval 1.8 to 8.6) for every kg increase in birth weight.

CONCLUSIONS

Essential hypertension is initiated in fetal life. A raised blood pressure is then amplified from infancy to old age, perhaps by a positive feedback mechanism.

The relation of maternal weight to the blood pressures of Gambian children

The objective of the study was to relate blood pressure levels in children to their mother's weight in pregnancy. The blood pressures of 675 children aged from one to nine years in three villages in rural Gambia were measured. They were matched to antenatal clinic data which had been collected from all pregnant women in the three villages since 1980. Among children under eight years of age those born in the dry season had the highest blood pressures and were heavier. Their blood pressures were positively related to body weight and to mothers' weight at six months of pregnancy. These relationships were independent of mothers' age and parity, birthweight, gestational age, and placental weight. Among older children, aged eight and nine years, those born in the rainy season had the highest blood pressures. Their blood pressures were not related to their mothers' weight at six months of pregnancy. Rather they were inversely related to mothers' weight gain in the last trimester. An interpretation of these findings is that among young children differences in blood pressure are largely determined by rates of maturation. However, the long-term effects of adverse intra-uterine influences which elevate blood pressure become apparent in older children.