Widespread occurrence of pesticides in low-income housing

Pesticide use, primarily in agriculture, poses significant exposure risks to certain populations. While most research focuses on agricultural settings, indoor pesticide exposure, particularly in low-income housing, remains understudied. Low-SES residents in social housing are disproportionately vulnerable due to factors such as structural deficiencies, poor maintenance, and inadequate pest control. These conditions lead to increased pest infestations and subsequent pesticide applications, negatively impacting indoor air quality and potentially causing adverse health outcomes. Children, pregnant women, and residents of low-quality housing are particularly susceptible to the harmful effects of pesticide exposure, given their higher inhalation rates, dust ingestion, and limited ability to escape exposure. Previous studies in the US have shown higher pesticide levels in low-income housing, highlighting this vulnerability. This study aimed to measure pesticide concentrations and exposures in low-SES social housing units in Toronto, Canada, a significant data gap given the limited Canadian data on indoor pesticide levels, and to identify factors associated with these exposures.

The literature highlights the disproportionate exposure of low-income populations to various indoor contaminants, including pesticides. Studies in Canada and elsewhere show that low-SES individuals experience higher exposures to pollutants compared to higher-SES individuals. Several US studies have documented elevated levels of both banned and current-use pesticides in low-income housing, often linked to poor housing quality. The persistence of pesticides indoors, due to reduced degradation pathways, further exacerbates the risk of prolonged exposure. The documented health risks associated with pesticide exposure include neurodevelopmental problems, cancers, and endocrine disruption. The Stockholm Convention and subsequent regulatory actions in Canada have led to restrictions and bans on several legacy pesticides, resulting in increased use of pyrethroids. Despite their perceived low acute toxicity, recent research points to potential adverse health effects from pyrethroid exposure, including reproductive issues and neurodevelopmental disorders in children.

This study involved sampling indoor air from 46 units across seven social housing multi-unit residential buildings (MURBs) in Toronto, Canada, constructed in the 1970s. Portable air cleaners equipped with high-efficiency media filters were deployed in each unit for one week in winter 2017. The filters were analyzed for 28 target pesticides from several classes: organochlorines, organophosphates, pyrethroids, strobilurins, and others. The study design ensured that buildings were located far from agricultural areas. A detailed analytical method involving extraction, cleanup using Florisil SPE cartridges, and gas chromatography-mass spectrometry (GC-MS) analysis was used. Quality assurance and quality control measures, including the use of labeled pesticide surrogates and blank samples, were employed. Chemical mass on the filters was converted to integrated air-particle concentration using gravimetric analysis, flow rate, and filtration efficiency. Gas-phase concentrations were estimated using the Harner-Bidleman equation. Data analysis included non-parametric tests due to non-normality of the data. Spearman rank correlation was used to evaluate co-usage of pesticides. The Mann-Whitney Wilcoxon test assessed differences in pesticide concentrations between smoking and non-smoking units.

At least one pesticide was detected in 89% of the sampled units. Current-use pyrethroids showed the highest detection frequencies (DF) and concentrations, with pyrethrin I reaching a maximum particle-phase concentration of 32,000 pg/m³. However, legacy organochlorines, such as heptachlor (banned in 1985), also exhibited high concentrations and DFs, with heptachlor showing the highest estimated maximum total air concentration (443,000 pg/m³). Concentrations of several pesticides (heptachlor, lindane, endosulfan I, chlorothalonil, allethrin, and permethrin) exceeded those reported in previous studies of low-income residences. The high DF of legacy OCPs highlights their persistence indoors. Tobacco smoking was significantly correlated with higher concentrations of five pesticides used on tobacco crops (chlorothalonil, permethrin, pyrethrin I, pyriproxyfen, and pendimethalin). The distribution of pesticides within individual buildings suggested that pest eradication programs and/or resident pesticide use were major sources. Significant correlations and co-occurrences were observed among several pesticides, indicative of co-usage and combined formulations.

The findings demonstrate widespread and significant exposure to various pesticides among low-SES residents in Toronto social housing. The high levels of both current-use and legacy pesticides, including those banned for residential use, highlight the persistence of these chemicals indoors and the vulnerability of this population. The association between tobacco smoking and pesticide concentrations underscores the multifaceted nature of indoor pollution. The data suggest that building management pest control programs and resident applications are primary sources of pesticide contamination, although the lack of information on pesticide application practices limits a definitive conclusion on the contribution of each source. The study's findings reinforce the need for integrated pest management strategies in social housing to reduce pesticide use and associated health risks. Addressing structural deficiencies and improving building maintenance are also crucial steps. Further research is needed to better understand the long-term health impacts of such widespread exposure.

This study provides the first comprehensive data on indoor pesticide levels in Canadian social housing, revealing widespread exposure to numerous pesticides, including both current-use and legacy compounds. The high concentrations of legacy pesticides highlight their persistent presence indoors. The correlation between tobacco smoking and pesticide levels emphasizes the multiple pathways of exposure in these vulnerable communities. These findings highlight the urgent need for improved pest management practices, building maintenance, and public health interventions to reduce pesticide exposure among residents of low-income housing.

The study's limitations include the lack of data on pesticide application practices by residents and building management, which hindered a precise quantification of each source's contribution. Air sampling was conducted near the ceiling to avoid resident inconvenience and tampering, potentially affecting the accuracy of exposure estimates. The absence of comparative data from higher-SES households prevents a direct comparison of exposure levels across different socioeconomic groups.