Nalini Sathiakumar

A follow-up study of synthetic rubber workers

Although 1,3-butadiene (BD) has been classified as an animal carcinogen, epidemiologic research has reported inconsistent results on the relationship between BD and lymphopoietic and other cancers in humans. This study evaluated the mortality experience of 15649 men employed for at least 1 year at any of eight North American styrene-butadiene rubber (SBR) plants. About 75% of the subjects were exposed to BD; 83% were exposed to styrene (STY). During 1943-1991, the cohort had a total of 386172 and an average of 25 person-years of follow-up, with 3976 deaths observed compared to 4553 deaths expected based on general population mortality rates (standardized mortality ratio (SMR) = 87, 95% confidence interval (CI) = 85-90). More than expected leukemia deaths occurred in the overall cohort (48 observed/37 expected, SMR = 131, CI = 97-174) and among ever hourly subjects (45/32, SMR = 143, CI = 104-191). The excess was concentrated among ever hourly subjects with 10+ years worked and 20+ years since hire (28/13, SMR = 224, CI = 149-323) and among subjects in polymerization (15/6.0, SMR = 251, CI = 140-414), maintenance labor (13/4.9, SMR = 265, CI = 141-453) and laboratories (10/2.3, SMR = 431, CI = 207-793), three areas with potential for relatively high exposure to BD or STY monomers. Some cohort sub-groups had slight increases in deaths from lymphopoietic cancers other than leukemia, but mortality patterns by race, years worked and process group within the SBR industry did not indicate a causal association with occupational exposures. These results indicate that exposures in the SBR industry cause leukemia.

A review of epidemiologic studies of triazine herbicides and cancer.

This is an update of a previous review of epidemiological evidence pertaining to the human carcinogenic potential of triazine herbicides. In 36 studies evaluated, atrazine was the most common triazine investigated. In general the studies were limited by lack of in-depth exposure measurements and by small numbers of subjects with potential high exposure and/or with many years of follow-up since first exposure. Non-Hodgkin lymphoma, prostate cancer, and breast cancer were most frequently investigated. Only one to three analytical or ecological studies investigated Hodgkin lymphoma, leukemia, multiple myeloma, soft tissue sarcoma, hairy-cell leukemia, melanoma, and cancers of the ovary, testes, colon, stomach, lung, brain, bladder, buccal cavity, and pharynx. Results of these studies were typically imprecise and did not form an adequate basis for determining if triazine exposure causes any form of cancer. Collectively, the available epidemiology studies do not provide consistent, scientifically convincing evidence of a causal relationship between exposure to atrazine or triazine herbicides and cancer in humans. Based upon the assessment studies, there is no scientific basis for inferring the existence of a causal relationship between triazine exposure and the occurrence of cancer in humans.

Cancer Incidence Among Triazine Herbicide Manufacturing Workers

This study evaluated cancer incidence and prostate specific antigen (PSA) testing among workers at a plant in Louisiana (LA) that made atrazine and other triazine herbicides. The study covered the time period 1985 through 1997 and included 2045 subjects, of whom 757 worked for the company that owned the plant and 1288 were contract employees. Linkage with a population-based cancer registry and review of death certificates and plant medical records identified cancer cases. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) compared subjects’ cancer incidence rates with those of a regional general population. Plant medical records provided data on the proportion receiving PSA tests among male company employees. Subjects had 46 observed and 40 expected cases of all cancers combined (SIR = 114, CI = 83–152) and had 11/6.3 prostate cancers (SIR = 175, CI = 87–312). The prostate cancer excess was greater in actively working company employees (5/1.3, SIR = 394, CI = 128–920) than in contract employees or inactive company employees (6/5.0, SIR = 119, CI = 44–260) and was limited to men under 60 years of age. Of the 11 prostate cancer cases, nine were diagnosed at an early clinical stage. From 1993 to 1999, the proportion of male company employees who had at least one PSA test was 86% for those who reached 40 years of age while actively working and was 98% for those who reached 45 years of age. The observed prostate cancer increase may have been due to the frequent PSA testing of actively working company employees. There is no epidemiologic or other information that clearly supports a causal relation between atrazine and prostate cancer.

Maternal mortality in Northern Nigeria: a population-based study

OBJECTIVES To determine the incidence and causes of maternal mortality as well as its temporal distribution over the last decade (1990-1999). STUDY DESIGN All maternal deaths recorded within the study period in the State of Kano, Northern Nigeria, were analyzed. Maternal mortality ratios (MMR) were computed using the Poisson assumption to derive confidence intervals around the estimates. A non-linear regression model was fitted to obtain the best temporal trajectory for MMR across the decade of study. RESULTS A total of 4154 maternal deaths occurred among 171,621 deliveries, yielding an MMR of 2420 deaths per 100,000. Eclampsia, ruptured uterus and anemia were responsible for about 50% of maternal deaths. CONCLUSION We found one of the highest maternal mortality ratios in the world. Maternal mortality could be reduced by half at study site with effective interventions targeted to prevent deaths from eclampsia, ruptured uterus and anemia.

Descriptive Epidemiology of Somatising Tendency: Findings from the CUPID Study

Somatising tendency, defined as a predisposition to worry about common somatic symptoms, is importantly associated with various aspects of health and health-related behaviour, including musculoskeletal pain and associated disability. To explore its epidemiological characteristics, and how it can be specified most efficiently, we analysed data from an international longitudinal study. A baseline questionnaire, which included questions from the Brief Symptom Inventory about seven common symptoms, was completed by 12,072 participants aged 20–59 from 46 occupational groups in 18 countries (response rate 70%). The seven symptoms were all mutually associated (odds ratios for pairwise associations 3.4 to 9.3), and each contributed to a measure of somatising tendency that exhibited an exposure-response relationship both with multi-site pain (prevalence rate ratios up to six), and also with sickness absence for non-musculoskeletal reasons. In most participants, the level of somatising tendency was little changed when reassessed after a mean interval of 14 months (75% having a change of 0 or 1 in their symptom count), although the specific symptoms reported at follow-up often differed from those at baseline. Somatising tendency was more common in women than men, especially at older ages, and varied markedly across the 46 occupational groups studied, with higher rates in South and Central America. It was weakly associated with smoking, but not with level of education. Our study supports the use of questions from the Brief Symptom Inventory as a method for measuring somatising tendency, and suggests that in adults of working age, it is a fairly stable trait.

Patterns of multisite pain and associations with risk factors

Summary In a large cross‐sectional survey, pain affecting 6–10 anatomical sites showed substantially different associations with risk factors from pain limited to 1–3 sites. ABSTRACT To explore definitions for multisite pain, and compare associations with risk factors for different patterns of musculoskeletal pain, we analysed cross‐sectional data from the Cultural and Psychosocial Influences on Disability (CUPID) study. The study sample comprised 12,410 adults aged 20–59 years from 47 occupational groups in 18 countries. A standardised questionnaire was used to collect information about pain in the past month at each of 10 anatomical sites, and about potential risk factors. Associations with pain outcomes were assessed by Poisson regression, and characterised by prevalence rate ratios (PRRs). Extensive pain, affecting 6–10 anatomical sites, was reported much more frequently than would be expected if the occurrence of pain at each site were independent (674 participants vs 41.9 expected). In comparison with pain involving only 1–3 sites, it showed much stronger associations (relative to no pain) with risk factors such as female sex (PRR 1.6 vs 1.1), older age (PRR 2.6 vs 1.1), somatising tendency (PRR 4.6 vs 1.3), and exposure to multiple physically stressing occupational activities (PRR 5.0 vs 1.4). After adjustment for number of sites with pain, these risk factors showed no additional association with a distribution of pain that was widespread according to the frequently used American College of Rheumatology criteria. Our analysis supports the classification of pain at multiple anatomical sites simply by the number of sites affected, and suggests that extensive pain differs importantly in its associations with risk factors from pain that is limited to only a small number of anatomical sites.

An updated study of mortality among North American synthetic rubber industry workers

Aim: This study evaluated the mortality experience of workers from the styrene-butadiene industry. Methods: The authors added seven years of follow up to a previous investigation of mortality among 17 924 men employed in the North American synthetic rubber industry. Analyses used the standardised mortality ratios (SMRs) to compare styrene-butadiene rubber workers’ cause specific mortality (1943–98) with those of the United States and the Ontario general populations. Results: Overall, the observed/expected numbers of deaths were 6237/7242 for all causes (SMR = 86, 95% CI 84 to 88) and 1608/1741 for all cancers combined (SMR = 92, 95% CI 88 to 97), 71/61 for leukaemia, 53/53 for non-Hodgkin’s lymphoma, and 26/27 for multiple myeloma. The 16% leukaemia increase was concentrated in hourly paid subjects with 20–29 years since hire and 10 or more years of employment in the industry (19/7.4, SMR = 258, 95% CI 156 to 403) and in subjects employed in polymerisation (18/8.8, SMR = 204, 95% CI 121 to 322), maintenance labour (15/7.4, SMR = 326, 95% CI 178 to 456), and laboratory operations (14/4.3, SMR = 326, 95% CI 178–546). Conclusion: The study found that some subgroups of synthetic rubber workers had an excess of mortality from leukaemia that was not limited to a particular form of leukaemia. Uncertainty remains about the specific agent(s) that might be responsible for the observed excesses and about the role of unidentified confounding factors. The study did not find any clear relation between employment in the industry and other forms of lymphohaematopoietic cancer. Some subgroups of subjects had more than expected deaths from colorectal and prostate cancers. These increases did not appear to be related to occupational exposure in the industry.

Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study

BackgroundPossible physiological causes for the effect of sunlight on mood are through the suprachiasmatic nuclei and evidenced by serotonin and melatonin regulation and its associations with depression. Cognitive function involved in these same pathways may potentially be affected by sunlight exposure. We evaluated whether the amount of sunlight exposure (i.e. insolation) affects cognitive function and examined the effect of season on this relationship.MethodsWe obtained insolation data for residential regions of 16,800 participants from a national cohort study of blacks and whites, aged 45+. Cognitive impairment was assessed using a validated six-item screener questionnaire and depression status was assessed using the Center for Epidemiologic Studies Depression Scale. Logistic regression was used to find whether same-day or two-week average sunlight exposure was related to cognitive function and whether this relationship differed by depression status.ResultsAmong depressed participants, a dose-response relationship was found between sunlight exposure and cognitive function, with lower levels of sunlight associated with impaired cognitive status (odds ratio = 2.58; 95% CI 1.43–6.69). While both season and sunlight were correlated with cognitive function, a significant relation remained between each of them and cognitive impairment after controlling for their joint effects.ConclusionThe study found an association between decreased exposure to sunlight and increased probability of cognitive impairment using a novel data source. We are the first to examine the effects of two-week exposure to sunlight on cognition, as well as the first to look at sunlights effects on cognition in a large cohort study.

Acute health effects of the Tasman Spirit oil spill on residents of Karachi, Pakistan

BackgroundOn July 27 2003, a ship carrying crude oil run aground near Karachi and after two weeks released 37,000 tons of its cargo into the sea. Oil on the coastal areas and fumes in air raised health concerns among people. We assessed the immediate health impact of oil spill from the tanker Tasman Spirit on residents of the affected coastline in Karachi, Pakistan.MethodsWe conducted a study consisting of an exposed group including adults living in houses on the affected shoreline and two control groups (A and B) who lived at the distance of 2 km and 20 km away from the sea, respectively. We selected households through systematic sampling and interviewed an adult male and female in each household about symptoms relating to eyes, respiratory tract, skin and nervous system, smoking, allergies, beliefs about the effect on their health and anxiety about the health effects. We used logistic regression procedures to model each symptom as an outcome and the exposure status as an independent variable while adjusting for confounders. We also used linear regression procedure to assess the relationship exposure status with symptoms score; calculated by summation of all symptoms.ResultsOverall 400 subjects were interviewed (exposed, n = 216; group A, n = 83; and group B, n = 101). The exposed group reported a higher occurrence of one or more symptoms compared to either of the control groups (exposed, 96% vs. group A, 70%, group B 85%; P < 0.001). Mean summary symptom scores were higher among the exposed group (14.5) than control group A (4.5) and control group B (3.8, P < 0.001). Logistic regression models indicated that there were statistically significant, moderate-to-strong associations (Prevalence ORs (POR) ranging from 2.3 to 37.0) between the exposed group and the symptoms. There was a trend of decreasing symptom-specific PORs with increase in distance from the spill site. Multiple linear regression model revealed strong relationship of exposure status with the symptoms score (β = 8.24, 95% CI: 6.37 – 10.12).ConclusionResults suggest that the occurrence of increased symptoms among the exposed group is more likely to be due to exposure to the crude oil spill.

Chemical exposures in the synthetic rubber industry and lymphohematopoietic cancer mortality.

Objective: This study evaluated the association between exposure to several chemicals and mortality from lymphohematopoietic cancer (LHC) among 16,579 synthetic rubber industry workers who were followed up from 1943 to 1998. Methods: Poisson regression analyses examined LHC rates in relation to butadiene, styrene, and DMDTC exposure. Models provided maximum likelihood estimates of the relative rate for the contrast between categories of one agent, adjusting for other agents and for additional potential confounders. Results: Cumulative exposure to 1,3-butadiene was associated positively with all leukemia (relative rates of 1.0, 1.4, 1.2, 2.9, and 3.7, respectively, for exposures of 0, >0 to <33.7, 33.7 to <184.7, 184.7 to <425.0, and 425.0+ ppm-years), chronic myelogenous leukemia and to a lesser extent with chronic lymphocytic leukemia. Adjusting for styrene and DMDTC attenuated these associations. After controlling for butadiene, neither styrene nor DMDTC displayed a consistent exposure–response trend with all leukemia, chronic myelogenous leukemia, or chronic lymphocytic leukemia. Conclusions: This study found a positive association between butadiene and leukemia that was not explained by exposure to other agents examined.