Carbon monoxide exposure in pregnant women in the UK

Background

Carbon monoxide (CO) is a colourless, odourless gas that poses a threat to life at concentrations of just a few hundred ppm. The developing foetus is particularly vulnerable to CO exposure, and maternal exposure to much lower levels of the gas is associated with adverse outcomes such as low birth weight. This study aimed to quantify CO exposure in pregnant women’s homes and assess whether breath CO levels could be linked to home-based CO exposure and sociodemographic factors.

Methods

CO levels were monitored continuously over two weeks in 161 households selected for indicators of lower socio-economic status and proximity to gas appliances, a risk factor for environmental CO exposure. Exhaled breath CO measurements were taken before and after the monitoring period.

Results

Of the households monitored, positive CO readings were detected in 57.8%, with 31.7% recording levels above 4ppm and 14.3% above 10ppm. CO exposure varied significantly across households, with both intermittent and prolonged exposures observed. Six households included in the study exceeded current World Health Organisation recommended limits of 3.5ppm for ≥ 24 h, and three exceeded the limit of 9ppm for ≥ 8 h. Higher CO levels in the household were associated with the use of gas for cooking. Higher exhaled CO levels were associated with number of smokers in the household and eligibility for the UK government NHS Healthy Start scheme. Following the monitoring period, exhaled CO levels were only associated with number of smokers in the household, suggesting an intervention effect.

Conclusions

This study indicates that exposure of pregnant women to CO within the home occurs predominantly within current recommended safe limits, and that exposure is linked to the use of gas appliances, socio-economic factors and smoking. This study highlights the need for improved CO monitoring and mitigation strategies, particularly in vulnerable populations, to protect maternal and foetal health.

What is it about?

The study aimed to quantify carbon monoxide (CO) exposure in the homes of pregnant women and assess its correlation with breath CO levels and sociodemographic factors. It monitored CO levels continuously for two weeks in 161 households. The study found that 57.8% of households had positive CO readings, with 31.7% exceeding levels of 4ppm and 14.3% exceeding 10ppm. Six households surpassed the World Health Organization's recommended limits for CO exposure. The study identified that higher household CO levels were associated with the use of gas for cooking, while higher exhaled CO levels correlated with the number of smokers in the household and eligibility for the UK healthy start scheme. After the monitoring period, only the number of smokers in the household was linked to exhaled CO levels, indicating a potential intervention effect. The findings suggest that CO exposure within the home is predominantly within recommended safe limits, with a few households exceeding this level, and that CO exposure within the home is influenced by gas appliances.

Why is it important?

This study is important as it sheds light on the environmental and health risks associated with carbon monoxide (CO) exposure in pregnant women, particularly from non-smoking sources like household gas appliances. It emphasizes the vulnerability of the developing foetus to CO exposure and the potential for adverse pregnancy outcomes, even at lower exposure levels. The study's focus on socio-economic factors highlights the need for targeted interventions in at-risk populations to mitigate CO exposure, thus underscoring the public health significance of addressing CO monitoring and awareness as a preventive measure to protect maternal and foetal health.

Key Takeaways:

1. Household CO Exposure: The study finds that CO exposure in pregnant women’s homes is often linked to the use of gas appliances, with significant variations in exposure levels, some exceeding WHO guidelines.

2. Sociodemographic Influences: Higher exhaled CO levels correlate with the number of smokers in the household and eligibility for the UK Healthy Start scheme, indicating socio-economic factors play a role in CO exposure risks.

3. Need for Intervention: The findings suggest that although most exposures are within current safe limits, there is a need for improved CO monitoring and mitigation strategies, particularly in vulnerable populations, to prevent potential adverse health outcomes.