Assessment of impact on health of residents living near the Nant-y-Gwyddon landfill site: retrospective analysis

Abstract

Objectives

To compare indices of health in a population living near a landfill site with a population matched for socioeconomic status and to review environmental monitoring data.

Design

Ecological study with small area statistics and environmental reports.

Setting

Electoral wards in valleys of South Wales.

Subjects

Populations in the five wards near the landfill site who had formally complained of odours (exposed population), and comparison populations in 22 wards in the same unitary authority within the same fifth of Townsend score.

Outcome measures

Mortality, rates of hospital admission, measures of reproductive health (proportion of all births and stillbirths of infants weighing <2500 g; rates of admissions for spontaneous abortion; rates of all reported congenital malformations). Environmental data on site emissions.

Results

There were no consistent differences in mortality, rates of hospital admissions, or proportion of low birthweight infants between the two populations. There was an increased maternal risk of having a baby with a congenital abnormality in residents near the site, both before its opening (relative risk 1.9; 95% confidence interval 1.3 to 2.85; P<0.001) and after (1.9; 1.23 to 2.95; P=0.003 ). Environmental monitoring showed that hydrogen sulphide from the site was probably responsible for odours.

Conclusions

The area surrounding the landfill site has an increased rate of reported congenital malformations, which predated the opening of the landfill, although the cluster of cases of gastroschisis postdated its opening. Several chemicals emitted from the site, including hydrogen sulphide and benzene, were found in air samples in the nearby community. Further studies of the reproductive risk in such communities are needed to examine the safety of waste disposal sites.

Introduction

Recent work has suggested that women living near landfill sites that receive hazardous waste have an increased risk of having a baby with congenital malformations,¹ but the potential risk from sites that receive only domestic, commercial, and industrial waste has not been examined adequately.

In 1996 residents living in the wards near the Nant-y-Gwyddon landfill site voiced increasing concerns that odours from the landfill site were causing illnesses. Symptoms and diseases they associated with exposure included stress, fatigue, headaches, eye infections or irritation, coughs, stuffy nose, dry throat and nausea, sarcoidosis, asthma, gastroschisis, and spontaneous abortions.

The Nant-y-Gwyddon landfill site, covering 24 hectares, was opened in January 1988 within 3 km of a population of 20 000 (fig 1). The local authority licence allowed the disposal of household, commercial, and industrial waste, and by 1996 about 850 000 m³ of waste, including calcium sulphate filter cake, had been deposited on the site.

Figure 1.

Five wards surrounding Nant-y-Gywddon landfill site in the Rhondda Valley, South Wales: the “exposed” wards

We assessed the health of the population living near the site using existing available epidemiological and environmental data. At the same time further monitoring of site emissions was carried out. We assessed, firstly, whether there was a difference in age standardised rates of death (all cause, respiratory, and cancers), rates of hospital admissions (general medical and geriatric, all respiratory disease, and asthma), and indices of reproductive health between the population living in the five wards near the landfill site compared with 22 other wards of similar socioeconomic level in the same unitary authority, before and after the site opened, and, secondly, whether there was evidence from previous environmental monitoring or from the concurrent environmental study of site emissions reaching the community.

Methods

Formal complaints to the environmental department of the local authority and to the environment agency were reviewed, and residents belonging to RANT (residents against Nant-y-Gwyddon tip) were visited. Hypotheses were formed from the specific disease concerns of the residents. The exposed population was defined as residents living in the five electoral wards within 3 km of the landfill site and from which complaints had been received from residents (fig 1). The comparison population comprised 22 other electoral wards in the same local authority, matched by fifths of Townsend score calculated from the 1991 census. The mean Townsend score of 1.92 for the exposed wards indicated slightly less deprivation than in the unexposed wards (2.28). We sought to obtain the most recently available data and historical data back to 1981, which was seven years before the site opened (table).

Data collection

Mortality by electoral ward from all causes, respiratory disease, and cancers was directly standardised to the European standard population, and trends in mortality in exposed and unexposed wards were compared. Rates of hospital admission were analysed by primary diagnosis on death or discharge. By using the international classification of diseases, 9th and 10th revisions (ICD-9 and ICD-10), we compared the rates in the exposed and unexposed wards for all general medical admissions (Korner specialty code 300), respiratory disease (ICD-9 codes 485-519; ICD-10 codes J10-99), asthma (ICD-9 code 493; ICD-10 code J45-6), cancer (ICD-9 codes 140-239; ICD-10 codes C00-97), sarcoidosis (ICD-9 code 135; ICD-10 code D86), and spontaneous abortions (ICD-9 code 634; ICD-10 code 003).

All babies born with at least one recorded congenital malformation on the register of the Office for National Statistics² and born to mothers resident in the 27 wards were examined in the categories of all congenital abnormalities and anomalies of the abdominal wall (1983-96; ICD-9 code 756.7; ICD-10 codes Q79.2, Q79.3, Q79.4.) Before 1995 the coding of the congenital malformation data did not differentiate between gastroschisis, exomphalos, or prune belly, and all were coded as midline abdominal wall defects. In 1990 the Office for National Statistics changed the reporting categories of congenital malformation, leading to a subsequent fall in the number reported nationally.

Numbers of therapeutic abortions performed for grounds E of the Abortion Act 1967 (a legally induced abortion when there is a substantial risk that if the child were born it would suffer from such physical or mental abnormality as to be seriously handicapped) available for 1992-6 were reviewed by the data custodians of the Welsh Office.

Analysis

The χ² test was used to test the association between the incidence of congenital malformations occurring in live and stillborn babies in the exposed and unexposed wards for the years before and after the site opened. The expected number of midline abdominal defects was calculated from the incidence of notified congenital abdominal wall defects in England and Wales between 1987 and 1993.³ The standardised ratio of observed to expected was calculated with 95% confidence intervals with CIA software,⁴ and Poisson cumulative probabilities were also calculated.⁵

Diagnoses made in general practice or hospital outpatient departments are not routinely available, and up to date cancer registrations for Wales were not available. We examined prescribing data available for 1996-7, but these were recorded only by the prescribing practice, not by electoral ward, and are not presented here.

Environmental monitoring

Two previous environmental monitoring studies commissioned by the local authority were reviewed. In 1997 further environmental monitoring was commissioned by the environment agency to quantify emissions from the landfill surface and to monitor air quality in the community during odour episodes.⁶

Results

From 1983-96 there were 302 children born in the 27 study wards with at least one registered congenital anomaly; the rate of congenital anomalies per 1000 total births in the exposed wards was higher in all but two years (fig 2). From 1983 to 1987 (before the site opened) and from 1990 to 1996 (after the site opened) the rate of congenital malformations in the exposed areas was 1.9 times the rate in the unexposed area (95% confidence interval 1.3 to 2.9, P⩽0.001; and 1.2 to 3.0, P=0.003, respectively). For 1988 and 1989, when the site was being developed and first used, the rate of congenital malformation in the five exposed wards was 3.6 times that in the unexposed wards (2.3 to 5.7, P<0.001). The discrepancy in the rates of births with congenital malformation between the exposed and the unexposed wards was not accounted for by an increased number of abortions (on grounds E) in the unexposed wards.

Figure 2.

 Rate of births with congenital malformation per 1000 total births in “exposed” and comparison wards

In the study wards from 1983-96 there were nine cases of midline abdominal wall defect identified in the register of the Office for National Statistics, seven of these occurring since 1991 (four in the exposed wards and three in the unexposed). Of the seven cases recorded by the register since 1991, the original paper notifications reported five cases of gastroschisis (four in the exposed wards and one in the unexposed wards) and two cases of exomphalos in the unexposed wards.

The incidence of notified congenital abdominal wall defects in England and Wales indicated an expected number of 0.45 cases in the exposed wards between 1989-96. Four cases were noted in data from the Office for National Statistics, giving a standardised ratio of 8.89 (2.42 to 22.8). The Poisson cumulative probability was 0.001. There were three cases observed in the unexposed wards compared with an expected 2.38, giving a standardised ratio of 1.26 (0.26 to 3.68). The Poisson cumulative probability was 0.3.

Annual mortality for all causes, respiratory disease, and cancer from 1981 to 1995 did not differ between the exposed and unexposed wards, neither did rates of hospital admissions for general medical conditions, respiratory diseases, asthma, spontaneous abortions, or cancers from 1991-2 to 1996-7 nor did the proportions of infants with births with low birth weight.

Environmental monitoring at the site, commisioned by the Environment Agency (ENTEC report⁶), identified various odours in the raw landfill gas, dominated by high levels of hydrogen sulphide. Several other compounds in the raw landfill gas—styrene, dimethyl styrene, ethyl benzene, and C4 alkyl benzenes—were found at concentrations exceeding those reported at other UK sites.

Between 24 July 1997 and 22 September 1997 the Environment Agency received 106 complaints of odours, all from residential areas close to the site boundary. On 24 of these occasions community air samples were taken to measure hydrogen sulphide concentrations, and on four occasions when odours were verified on call out, air samples were sent for more detailed analysis. On three of these four occasions benzene exceeded the environmental assessment limits developed by the Environment Agency. Hydrogen sulphide was recorded above its odour recognition threshold (3.5 μg/m³) on nine of the 24 call outs. The maximum concentration (20 μg/m³) was above the World Health Organisation's sensory annoyance guideline (7 μg/m³) but did not exceed its occupational exposure standard for non-occupational settings. Continuous monitoring of hydrogen sulphide was undertaken between 9 and 16 September and on 31 October and 1 November at two sites at 500-1000 m from the landfill. The WHO sensory annoyance guideline was exceeded during the evening of 15 September. The composition of the raw landfill gas and the community samples suggested that the landfill was the source of the hydrogen sulphide.

Discussion

In response to community concerns we reviewed the guidelines for conducting public health assessments near landfill sites, developed by the US Agency for Toxic Substances and Diseases Registry,⁷ which recommend evaluation of the site for evidence of exposure to hazardous substances before any further work is undertaken. In the United Kingdom the availability of population based, routine health data offers a potentially important alternative public health approach. Indeed, the public usually expects an early analysis of these data.

Reproductive health outcomes

We consulted with the residents and local agencies to agree the categories of ill health to be studied. To control for the confounding effects caused by socioeconomic factors we compared the five wards nearest to the landfill site with 22 others in the same unitary authority matched for Townsend deprivation score. The main finding was an increase in rates of congenital malformations. Although the Office for National Statistics recognises that the data on congenital malformations are not always accurate or complete,² we have no reason to suppose that the data for the five exposed wards are any different in quality to those for the 22 unexposed wards. The incidence of all congenital malformations was raised in the exposed wards both before and after the site opened in 1988 (relative risk both 1.9). This is an important observation as other studies have noted an association between congenital malformations and living near hazardous waste sites.¹,⁸ One low powered case-control study near a municipal waste site did not detect any increased risk for spontaneous abortions, stillbirths, or birth defects,⁹ but within 4 km of a large municipal waste site Goldberg et al found an excess of between 11% and 20% in low birth weight and between 8% and 13% more babies who were small for gestational age.¹⁰ We agree with Dolk et al that there is an urgent need for further studies of landfill sites,¹ and we suggest examination of rates in the area both before and after a site becomes operational.

What is already known on this subject

Recent studies have noted an association between the birth prevalence of congenital malformations and living near hazardous waste sites

Few studies have examined municipal landfill sites

What this paper adds

This retrospective analysis showed that residents living near a landfill site had an increased risk of having a baby with a congenital malformation, not only after the site became operational but also before

There was also a cluster of gastroschisis

Protocols should be developed to measure community exposures systematically as public concern about environmental exposures and their health effects is increasing

Community observations about an increase in gastroschisis were confirmed; the incidence of anterior abdominal wall defects (which include gastroschisis) was unusually high compared with the rest of England and Wales. All abdominal wall defects in the exposed wards since 1989 were confirmed as gastroschisis, whereas two of the three abdominal wall defects in the unexposed wards were exomphalos. Gastroschisis has a higher prevalence in young mothers,¹¹but the occurrence of four cases in the exposed wards would be unusual even if all the births from 1989-96 had been to teenage mothers (standardised ratio 4.8; 1.6 to 11.1). We recognise that the identification of the cluster has limited implications as it resulted from a post hoc analysis but the findings justify further analytical study in the area. The birth prevalence of gastroschisis seems to be increasing nationally and internationally,¹² and further studies of aetiology are required urgently.

Community environmental exposures

The evaluation of any health effects was hampered by no direct measures of exposure, no biomarkers, and no community monitoring during the peak of the problem. The ENTEC study was carried out while the site was not accepting waste and while the landfill gas control systems were being modified. A number of potentially toxic chemicals, including sulphuretted and aromatic compounds, were identified at high concentrations in the raw landfill gas and the gas immediately above the site. Hydrogen sulphide is not known to cause developmental defects,¹³but the occasional high concentrations of hydrogen sulphide found in community air samples were consistent with complaints of headaches, eye irritation, and sore throats. The monitoring in the community that was undertaken was limited in scope as it measured only hydrogen sulphide on most occasions with detailed analyses undertaken on only four occasions. Modelling work on atmospheric dispersion undertaken by ENTEC, which used values after remedial work had started, suggested that landfill gas might contribute up to 1.1 ppb in the community air samples during monitored odour events. We recommend that protocols be developed to measure community exposures systematically near landfill sites.

Table.

Source of data for impact on health of living near landfill site

Content	Dates	Source
Congenital malformations	1983-96	Office for National Statistics (ONS)
Townsend scores population denominators	1991	ONS census data held by Bro Taf Health Authority
Total births	1988-96	Birth notifications to Bro Taf Health Authority
No with low birth weight	1988-96
Congenital anomalies	1997
Total births	1983-87	Small area health statistics unit
All cause deaths	1981-95	ONS death notifications held by the Welsh Health Common Services Authority
Respiratory deaths	1981-95
Neoplastic disease	1981-95
Hospital admissions	1991-7	Patient episode database for Wales
Therapeutic abortions	1992-6	ONS analysed by Welsh Office