Nitrate contamination in drinking water and colorectal cancer: Exposure assessment and estimated health burden in New Zealand.

BACKGROUND: Epidemiological evidence in multiple jurisdictions has shown an association between nitrate exposure in drinking water and an increased risk of colorectal cancer (CRC). OBJECTIVE: We aimed to review the extent of nitrate contamination in New Zealand drinking water and estimate the health and financial burden of nitrate-attributable CRC. METHODS: We collated data on nitrate concentrations in drinking water for an estimated 85% of the New Zealand population (∼4 million people) who were on registered supplies. We estimated nitrate levels for the remaining population (∼600,000 people) based on samples from 371 unregistered (private) supplies. We used the effective rate ratio from previous epidemiological studies to estimate CRC cases and deaths attributable to nitrate in drinking water. RESULTS: Three-quarters of New Zealanders are on water supplies with less than 1 mg/L NO3-N. The population weighted average for nitrate exposure for people on registered supplies was 0.49 mg/L NO3-N with 1.91% (95%CI 0.49, 3.30) of CRC cases attributable to nitrates. This correlates to 49.7 cases per year (95%CI 14.9, 101.5) at a cost of 21.3 million USD (95% 6.4, 43.5 million USD). When combining registered and unregistered supplies, we estimated 3.26% (95%CI 0.84, 5.57) of CRC cases were attributable to nitrates, resulting in 100 cases (95%CI 25.7, 171.3) and 41 deaths (95%CI 10.5, 69.7) at a cost of 43.2 million USD (95%CI 10.9, 73.4). CONCLUSION: A substantial minority of New Zealanders are exposed to high or unknown levels of nitrates in their drinking water. Given the international epidemiological studies showing an association between cancer and nitrate ingestion from drinking water, this exposure may cause an important burden of preventable CRC cases, deaths, and economic costs. We consider there is sufficient evidence to justify a review of drinking water standards. Protecting public health adds to the strong environmental arguments to improve water management in New Zealand.

Issues in the assessment of cardiovascular risk in selected general practices in Canterbury, New Zealand.

AIMS: The aim was to audit patient records at selected general practices in Canterbury, New Zealand to assess the potential: (a) to improve identification and management of people with risk factors for cardiovascular disease (CVD); and (b) to develop a geographically distinct community database of CVD risk factor prevalence that could be used to plan public health programmes to improve cardiovascular health. METHODS: Patient records were audited in three general practices in a Canterbury rural town and information on cardiovascular risk factors recommended for the screening and management of CVD by the New Zealand Guidelines Group was extracted and entered into an electronic database. The data was analysed to assess the extent of recording of information on recommended risk factors. RESULTS: Most patient records contained information on smoking, blood pressure and lipid profiles. Low levels of information recording were found for physical activity, body mass index (BMI), and family history. There were statistically significant differences between general practices in the type and coverage of information recorded, even for patients with diagnosed cardiovascular disease. Because of deficiencies in information, it was not possible to calculate CVD risk using the guidelines for 43% of patients. Some practices remain reliant on paper records which make it extremely difficult to undertake a systematic programme of screening and management of CVD risk factors. CONCLUSIONS: Before it is practical to undertake a systematic screening programme for CVD risk factors in primary care, it is necessary to reduce reliance on paper records and to fully implement computerised patient management systems that allow for information storage and retrieval. In addition, it is essential to improve the systematic collection of key information in primary care that is used to assess risk of CVD.