Impact of sanitation system types on residential and environmental presence of human waste and parasites in Alabama

Abstract

Lowndes County is a predominantly Black rural county in Alabama, in the United States, which has a historical and current legacy of racial discrimination, creating inequitable infrastructure access and adverse health impacts. Over 80% rely on on-site sanitation infrastructure and most are failing. A community assessment of exposure to untreated sewage was conducted using samples from residential drinking water, surface swabs, and soil combined with environmental water and soil samples using culture-based and quantitative polymerase chain reaction (qPCR) methods. Testing varied slightly across samples, due to difficulty of access or availability. Of 43 households, 68% and 55% of houses had detectable presence of human fecal matter indicator in their soils and on their doorsteps, respectively, and 0% had detectable amounts of culturable Escherichia coli in their drinking water. Of 40 houses sampled, 88% tested positive for E. coli in soil samples. Of 39 residences, 31% had positive presence of environmental and zoonotic parasites in soil, but none for Necator americanus, Cryptosporidium species, or Giardia intestinalis. Of the 18 sampled environmental surface waters, 100% tested positive for culturable E. coli, 50% had detectable human fecal matter indicator present, and 27% tested positive for anthropogenic parasites. This work sheds light that there is presence of culturable E. coli, human fecal matter, and anthropogenic parasites in residential soil samples of all sanitation types (municipal, septic tank, and straight piping) and in environmental surface waters throughout the sampled areas. Our findings support the narrative that sanitation infrastructure of all types in Lowndes County, Alabama are compromised and highlights residential and environmental exposure to raw wastewater.

Keywords: Exposure; Infrastructure; Parasite; Sanitation; Waste.

Fig. 1

Proportion of houses which had detectable levels of Escherichia coli, HF183 and all parasites in residential soil samples

Fig. 2

Boxplots of quantifiable average Escherichia coli, HF183 and all parasites concentrations in residential soil samples; Samples that had values between the LOD and the LOQ are reported as 1 copy g⁻¹ soil;^▲outliers; ^**statistical significance (P < 0.01) from ANOVA test

Fig. 3

Proportion of houses which had detectable levels of Escherichia coli, HF183, and parasites all present in residential soil samples where all three contaminant types were sampled

Fig. 4

Proportion of houses which had detectable levels of Escherichia coli or HF183 in residential swab samples

Fig. 5

Boxplots of average quantifiable Escherichia coli or HF183 in residential swab samples. Samples that had values between the LOD and the LOQ are reported as 1 copy swab⁻¹; ^▲outliers

Fig. 6

Proportion of houses which had detectable levels of Escherichia coli or HF183 in residential swab samples for inside and outside doorsteps

Fig. 7

Boxplots of average quantifiable Escherichia coli or HF183 in residential swab samples for inside and outside doorstep; Samples above the qPCR limit of detection and below the limit of quantification are represented as 1 copy/swab; ^▲outliers; *statistical significance (P < 0.05) from ANOVA test

Fig. 8

Proportion of surface water samples which had detectable levels of Escherichia coli, HF183 and parasites for soil and water sub-component samples

Fig. 9

Boxplots of average quantifiable Escherichia coli, HF183 and parasites concentrations in surface water samples for soil and water sub-component samples. Samples above the qPCR limit of detection and below the limit of quantification are represented as 1 copy/g soil or 1 copy/100 ml water, ^▲outliers