PHOTO of sewage contamination leaking to a yard surface from a broken sewer pipe Do Sewage Pathogens & Contaminants Appear in Fruits and Vegetables Grown Near Septic Drainfields?
     

  • SEWAGE CONTAMINANTS in FRUIT / VEGETABLES - CONTENTS: Septic system contaminants: is it safe to eat fruits or vegetables grown over or close to septic systems? What are the risks of growing a garden, fruits, or other crops on or near septic wastewater disposal fields, drainfields, soakaway beds, or leaching trenches? How safe are the fruits of trees growing near septic soak beds or septic tanks?
  • POST a QUESTION or READ FAQs about gardens and fruit trees located close to septic systems
  • REFERENCES

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This document discusses the health hazards of consuming fruits and vegetables that may contain contaminants produced if they are grown over septic drainfields or too close to other sources of effluent from septic systems or on-site waste disposal systems

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Can Sewage Pathogens & Contaminants Appear at Unsafe Levels in Fruits and Vegetables Grown Near Septic Drainfields?

We include discussion of health or other concerns with soil and groundwater contamination and with measures adopted to address these problems. Our page top photo shows the author (DJF) inspecting a vegetable farm near Frankfort, Germany in 1968.

The short answer is yes, at least some contaminants and pathogens found in sewage and sewage effluent may be present in fruits and vegetables grown on or close to septic system components that deliberately (drainfields, cesspools, drywells) or accidentally (leaky septic tanks or broken septic or sewer piping) place septic or sewage effluent in soils near plants.

But like sewage effluent, the topic is a bit murky. While some studies found dangerous levels of sewage pathogens in wastewater and in crops ground therein, and while others warn of other non-biological contaminants (chemicals, pesticides, medicines), other researches describe successful growth of some food crops in some soils where wastewater, even sewage are applied. So unfortunately, as Mark Cramer says, " ... it depends".

On what? At least on a number of site conditions and seasonal, weather, and care or maintenance as well as design variables described here.

Studies such as the one described below did not find that all pathogens appear in fruits and vegetables grown over or near a septic drainfield. For example Staphylococcus aureum was not detected in the study below. But twenty-two other dangerous pathogens - enterobacteriaceae were indeed found. The vegetables tested in the study we discuss below were tomato, radish, cucumber, eggplant, potato, pepper, garden pea, gourd, zucchini, artichoke, broad bean, turnip, onion,
French bean, and lettuce.

In "Bacterial Pathogens Recovered from Vegetables Irrigated by Wastewater in Morocco", a study of the occurrence of pathogenic bacteria in vegetables irrigated by untreated wastewater, published in June 2007, Y. Karamoko et als, (quoting from the article abstract)

The authors obtained 50 vegetable samples from various regions in Morocco and examined them to determine the micro biological quality of these products. Aerobic count, coliform, enterococci, and Staphylococcus areus were evaluated. ...

The results clearly demonstrated that vegetables irrigated with untreated wastewater have a high level of microbiological contamination. ...

The large number of total microorganisms and fecal-contamination indicators (E. coli, coliform, and enterococci) detected in the vegetable samples we surveyed indicates a potential health hazard to consumers.

Also quoting from the above study,

Numerous reports have indicated that raw vegetables may harbor potential food borne pathogens (Beuchat, 1996). In particular, tomatoes, cantaloupes, and sprouts have been linked to outbreaks of salmonellosis (Guo, Chen, Brackett, & Beuchat, 2001), and outbreaks of illnesses caused by Escherichia coli O157:H7 have been associated with melon, apple eider, lettuce, and radish sprouts (Breuer el al., 2001).

Moreover, coleslaw, cabbage, potatoes, radishes, bean sprouts, and cucumbers contaminated with Listeria monocytogenes have been linked to disease outbreaks (Shearer, Strapp, & Joerger, 2001), and salad vegetables also may be contaminated with Campylobacter (Evans, Ribeiro,& Salmon, 2003). - all of these citations can be found at our References section.

The vector of contamination of fruits and vegetables from septic effluent includes multiple paths. The authors point out that ... vegetables can become contaminated with pathogenic organisms during growth, harvest, post harvest handling, or distribution (McMahon Sr Wilson, 2001). Use of untreated wastewater in irrigation represents an important route for transmission of these pathogenic organisms.

So does a private septic tank and drainfield adequately treat septic effluent so that it is not a risk to crops or fruits grown nearby? Effluent discharged from a septic tank is not "untreated" - rather it is "partly treated". It is not "fully treated". We interpret this to mean that while the risk of contamination of fruits and vegetables grown over or close to a septic drainfield may be less than that found in this study, it is certainly not zero.

The level of wastewater treatment by conventional septic tanks is typically less than 20% to no more than 45%. (Jantrania). Advanced wastewater treatment systems, if the system is properly installed, designed, maintained, and is working, can treat effluent more effectively to 70%.

Jantrania points out that small wastewater treatment systems can produce good results, capable of producing exceptional quality as good as large municipal wastewater treatment systems. While Jantrania (p. 5) asserts that "Complete recycling of wastewater to drinking water standards with onsite treatment is feasible", we pose that such a level of treatment at private onsite treatment systems (residential septic tanks, drainfields, even
AEROBIC SEPTIC SYSTEMS
,

or MEDIA FILTER SEPTIC SYSTEMS, and

other SEPTIC SYSTEM DESIGN ALTERNATIVES) in practical application rarely, perhaps never, reaches that standard except where special sterilizing equipment and systems are installed.

Below, abstracted from the Karamoko article, are the top six most frequent enterobacteriaceae found in the fruits and vegetables tested:

Enterobacteriaceae Recovered from Raw-Vegetable Analysis

(Excerpted from Table 2 in the above article. 22 Organisms are listed in the original)

Organism

Frequency*

Percentage **

Citrobacter freundii 28 18.7
Enterobacter cloacae 27 18.0
Klebsiella pneumoniae 17 11.3
Escherichia coli 1 16 10.7
Enterobacter sakazakii 12 8.0
Serratia liquefaciens 11 7.3

* Frequency o( strains In the 50 analyzed samples.
** Percentage of strains isolated.
Complete Table 1 from the study
Complete Table 2 from the study

Bacterial Pathogens from Septic Effluent Can Survive in Soil and Transfer through Vegetables to Humans

The authors Y. Karamoko et als, continued:

Madden has discussed potential sources of microbial contamination of fresh fruit and vegetables during growth, harvest, distribution, and processing (1992). The bacteria that the authors found on samples belonged most frequently to the Citrobacter- Enterobacter--Serratia group or Enterobacteriaceae. Although usually regarded as human pathogens, these members of Enterobacteriaceae family have also been recognized as inhabitants of soil and plants (Wright, Kominos, Ss Yee, 1976). Thus, vegetables may serve as a reservoir from which the bacteria named above can colonize and infect a susceptible host.

Our conclusion is that unless you have obtained specific and reliable tests indicating otherwise, consuming fruits or vegetables grown in soil fed by septic effluent pose a health risk.

Our OPINION is that the health risk from such foods ma be even more serious for people at extra risk due to fragile health, such as people whose immune systems are weakened or compromised, undergoing chemotherapy, for example, the elderly, infant, or people suffering from immune-related disorders. Discuss these risks with your doctor.

at BACTERIAL PATHOGENS in FRUIT & VEGETABLES is a slightly-rough online copy of the original article.

The Y. Karamokoet als, article discussed here is one of the most important contemporary research projects performed to study the risk of contaminants entering human food through wastewater. But interpreting the actual level of risk to a homeowner whose garden is close to or even atop a septic drainfield, and where raw sewage wastewater is not being used to directly irrigate fruits or vegetables, some important questions remain.

The questions that we pose below are intended to assist in translating the level of contamination found in the Y. Karamoko et als, study, "Bacterial Pathogens Recovered from Vegetables Irrigated by Wastewater in Morocco", Y. Karamoko, K. Ibenyassine, M. M. Ennaji, B. Anajjar, R. Ait Mhand, M. Chouibani, Journal of Environmental Health, June 2007, (wastewater irrigated plants) and the level of pathogens that might be expected to be found in fruits and vegetables grown over a common residential septic drainfield?

Question 1: How completely did the authors separate possible fruit/vegetable contaminant sources- plant root system vs. plant surfaces: contaminants arising through the soil and through a plant's root system need to be described separately from contaminants that may be lodged on the surface of a fruit or vegetable from dust, wet soil splash-up during rain, during handling?

The study cites indicates "The vegetable samples were collected in sterile polyethylene bags, and steps were taken to avoid contamination of the vegetables by soil or other contamination sources." and " Each sample was rinsed several times with sterile distilled water to eliminate the soil."

What might be unanswered is the effect of the duration of time that dust, or unsanitary water splash-up rested on plant surfaces before the plants were washed in the lab, and the extent to which pathogens may have been absorbed into the plant system through its surfaces rather than its root system.

Question 2: How do planting, soil specifics, plant root depths, septic drainfield design, high seasonal water table and type of plant affect the uptake of sewage contaminants into fruits or vegetables grown over a conventional septic drainfield compared with the uptake of sewage contaminants into these same plants when direct irrigation is performed using sewage or septic effluent?

The authors were aware of this question, as the study cites "The actual risk of disease transmission, however, is related to whether this survival time is long enough to allow transmission to a susceptible host. The crop and the field are the link between the pathogen in the wastewater and the potential for infection. The factors controlling transmission of disease are agronomic examples of such factors are the crop grown, the irrigation method used to apply wastewater, and cultural and harvesting practices. "

And "Guo and co-authors have demonstrated that soil and water are potential reservoirs from which Salmonella can contaminate tomatoes (Guo, Chen, Brackett, & Beuchat, 2002). ... That study provided evidence that Salmonellae can be transported from an inoculated nutrient solution to the hypocotyls, cotyledons, stems, and leaves of young tomato plants."

We understand the study to assert that dust and splash-up onto plant surfaces ("aerial tissues") could be a source of the pathogens found in the study, as well as roots "tissues in contact with inoculated soil".

This combination of pathogen sources may make it more difficult to translate the results of this study to a level of risk for plants grown over septic drainfields, systems where effluent is not being applied directly to the surface of soils but rather is being distributed underground.

Question 3: What assays were made of the level of contaminants in the irrigating sewage or septic effluent that was used to irrigate the studied fruits and vegetables?

We did not find this information included in the study except for a general description of the types of contaminants found in wastewater used for irrigation in many countries.

Question 4: What differences should we expect to find between the level of contaminants in the irrigating sewage or septic effluent used in the areas studied compared with the level of contaminants in private onsite septic system effluent flowing into a septic drainfield?

OPINION: This is the chief question that needs to be answered in extending the results of this important study to the question of the level of pathogens that may be found in garden vegetables or fruits planted over or close to a conventional septic system drainfield in which effluent is disposed-of entirely below ground.

OPINION: A second level of risk is likely to be found in alternative septic system designs (aerobic or ATU systems used for example in the Southwestern U.S.). Although aerobic ATUs achieve a higher level of treatment, in some private septic system designs the effluent from those systems is dispersed to the ground surface using sprays. The benefit of higher level of treatment of wastewater may be offset by its surface application if property owners grow edible foods nearby.

Factors Affecting Risk of Pathogenic Contamination of Vegetables or Fruits Grown over a Septic Drainfield

At Gardens Near Septics we stated that planting a fruit or vegetable garden over or near septic system components raises some important questions:

  • Will there be pathogenic or chemical contamination of the soil (bacteria, viruses, cleaners) below the garden?
  • Will septic system pathogens enter in or contaminate fruits or vegetables planted over or near the septic system?
  • Will chemicals or salts passing through the septic system harm nearby plants?
  • Will the garden planting itself harm the septic system in some way?

It seems likely that the following variables will affect the level of contaminants picked up by vegetables or fruits grown on or over private septic drainfields and effluent disposal systems:

  • The presence/absence of particular contaminants disposed-of into a particular onsite wastewater treatment unit, such as high levels of antibiotics, chemicals, or unusual pathogens - this is an unknown
  • Condition of the specific onsite treatment system or septic system: an older septic drainfield that is no longer working, pushing sewage effluent to or close to the yard surface, is at greater risk of contaminating not only plants growing over the drainfield, but any plantings that are down-slope from that area. Therefore original septic system design, septic system maintenance (SEPTIC TANK PUMPING SCHEDULE),

    and soil conditions are important factors in the health risks associated with nearby plantings.
    See SEPTIC DRAINFIELD LIFE and SOIL CONDITIONS.
  • The level of treatment of wastewater achieved by the septic tank or treatment unit - reasonable for conventional septic tanks is to presume no greater than 45% treatment in the tank, with an unknown level of additional treatment within the soils where wastewater is being discharged
  • The rate of discharge of wastewater into the system: a high-use septic system, possibly even used beyond its design point, can push wastewater into the septic tank or treatment system faster than treatment can take place, resulting in discharge of un-treated effluent or very limited treatment of effluent, before it is discharged into the absorption system, thus increasing the level of pathogens in the soil
  • Soil conditions and design of the wastewater absorption system: the distance between the bottom of the wastewater trenches of a drainfield and the seasonal high water table, soil percolation rates, soil chemistry, depth at which the wastewater is discharged (deeper means less oxygen means less aerobic bacterial action), age and condition of the system (is it exposed to periodic flooding?) and similar factors will affect not only the level of treatment achieved in the soils but the distance between septic effluent and the root system of the plants that may be present nearby or above.
  • Type, location, and specific species of plants near the septic system: plant systems vary by root depth, root characteristics, and other factors that are likely to affect the uptake of pathogens into the plant systems.

    At Gardens Near Septics we provide details such as plant type, root system type, and plant location and we offer some opinion about those effects on plant contamination by sewage pathogens.
  • Seasonal changes in soil conditions, level of septic system usage, effluent transpiration rate, and similar factors.

Septic "Treatment Chemicals" may Also be a Hazard to Nearby Fruits & Vegetables

OPINION: At USING ROOT KILLERS in SEPTIC FIELDS we discuss using chemicals to try to "clear" septic system piping and drainfields. These products include a range of chemicals whose product-description ranges from "safe and harmless" to "toxic -keep out of reach of children".

We have not yet found studies of toxic chemicals picked up by fruits and vegetables grown near septic systems from chemical treatment sources. Contact Us if you have information.

OPINION: A second category of possible "chemical " contaminants from sewage includes heavy metals that may be present in sewage or septic effluent.

See SEPTIC TREATMENTS & CHEMICALS for more information and warnings.

Readers should also see our safe-planting discussion at Gardens Near Septics and see our discussion of pathogens in sewage
at SEWAGE PATHOGENS in SEPTIC SLUDGE: what makes up the contents of residential sewage? and

also SEWAGE NITROGEN CONTAMINANTS - a second important type of septic effluent contamination.

Anyone working on or around or owning a septic tank should be sure to
see SEPTIC & CESSPOOL SAFETY.

We discuss the risk of tree or plant damage to septic drainfields
at SEPTIC SYSTEMS, PLANTS OVER.

What About Fruits & Vegetables Grown Near the Septic Tank Itself?

Question: what about medical chemicals that enter the septic tank and then the drainfield area?

(June 27, 2012) Anonymous said:

We have an old cerment drain septic tank ( about 40 years ols ) In haqve been having chemo treaztment every 2 weeks for the past 6 monrh. Would this cause damage to system

Reply:

Anon, thanks for the interesting question; we have found and provide citations that indicate that high levels of antibiotics in a septic tank can kill off bacteria enough to interfere with the tank's normal operation; but I don't know the effects of the chemicals in chemotherapy on a septic system.

We also don't know what happens to those chemicals when they pass out of the septic tank and into the drainfield. Normally I'd expect that any chemicals that do not deteriorate in the presence of soil bacteria and the limited oxygen there migrate down to local waterways or ultimately to the aquifer, presumably in quite diluted form. But we don't know what happens if a septic tank or drainfield contain high levels of chemicals and then are flooded.

If you are just one occupant in the household I suspect that the effects are minimal; if you're worried about it nonetheless, I recommend having the septic tank pumped at twice the normal pumping frequency for the tank size and number of users. Let's hope your treatment is finished soon and all related worries are done and over.

Question: If my avocado and mango trees are planted near, within three meters of my septic tank, are they safe to eat? -- Cheryl Sweetland

Answer: OPINION: Well, the answer is a definite "maybe". Or as ASHI Educator Mark Cramer says, "It depends."

In theory, a septic tank that is working correctly never overflows or floods. Sewage and septic effluent stay safely inside the tank and effluent flows out of the septic tank through solid piping (not perforated piping) to a drainfield or to a distribution box that then connects to the drainfield.

If your trees are a safe distance from the drainfield and if the septic tank is not leaky, and if no one spills sewage all around the tank during pumping, your mangos and avocados are probably fine to eat. at SEPTIC SYSTEMS, PLANTS OVER we discuss issues of planting anything over or near septic system components. If your trees are close to the septic tank there are two other risks:

  1. The tree roots may invade the septic tank or piping, leading to blockage or damage
  2. The tree roots may ultimately have to be cut to access or clean the septic tank, leading to a dead or sick tree.

If your septic tank is home-made or "site built" or if it is a cesspool, it is much more likely that tree roots will invade and damage the system and that fruit on those trees may be contaminated as well.

If you don't know where the drainfield is actually located on your property, it would be smart to find it. See SEPTIC DRAINFIELD LOCATION.

Safety of Fruits Grown on Trees Near Septic Tanks or Septic Drainfields

Reader Comment: A garden over a drainfield does not present the same risks as using sewage directly on crops - tree crops may be ok

I recently found your site and find it very useful. Being very interested and reasonably well educated in wastewater and reuse I found your review of the septic system and gardens interesting (I like fining new articles) but perhaps too conservative and too have missed an important point.

The Morocco paper refers to harvest of vegetables with untreated wastewater as you mention but most importantly the wastewater is applied at the soil surface. This is very different from growing a garden on top of a drainfield. In a well operating drainfield (i.e. no surfacing sewage) the septic tank effluent is well treated and will only be in contact with the plant roots.

A review of the literature shows that this mechanism of transport for pathogens into healthy plants is unlikely, particularly in tree crops.

Best regards, Peter Burgoon, PhD, P.E. Water Quality Engineering, Inc.[1]

Editor's note, quoting from WQE's website:
Water Quality Engineering, Inc (WQE) specializes in evaluation and design of processes that impact water quality in the rural and suburban landscape. Water Quality Engineering, Inc (WQE) specializes in evaluation and design of processes that impact water quality in the rural and suburban landscape.

Reply: Ok to grow food crops over a septic drainfield? It depends ...

Mr. Burgoon

Your angrily- put point about the lower risk of sewage pathogens in tree crops is nevertheless well taken, though that too may need some clarification. Your demand for a "concrete answer" without, as I would put it, any qualifications, is understandable (as simplistic answers are easier to digest you may be frustrated) but still the demand for a single "yes or no" answer is ill-advised.

For example in the case of some fruit crops (mangos, papaya) grown in Mexico and Central and South America there has long been a concern for and history of septic pathogens in [or on] those foods.

Testing those fruits for coliform or other contaminants is tricky because often they are harvested, transported, stored, and sold under dusty conditions during which contaminants may settle onto the skin or surface of the fruit even though contemporary growing conditions themselves may not be a source of contamination.

Certainly out of the U.S. it is good practice (and a commonly followed procedure) to wash all fruits and vegetables in a suitable disinfectant (we use SinBac®) before consuming them. This disinfection step removes contaminated surface dust or bacteria that may have been placed thereon by handling. [We discuss SinBac
at CHLORINE DISINFECTANT for Drinking Water]

The topic of what can be grown over a septic drainfield continues to interest many of our readers. My OPINION, for which I'd appreciate argument from you, is ... it depends.

Reader Comment: so can fruit trees filter toxins or not? Just tell me "yes" or "no" !

(Mar 24, 2012) kenboe said:

After reading this I have seen no scientific claim that eating fruit from a tree whom's roots draw water from a septic field directly will transmit chemical, bacterial, or viral toxins to the fruit. You obfuscate like a lawyer around the issue without courage or directness. You clearly state that your studies were on vegetables that grow low to the ground in irrigated soil which is a whole different kind of exposure to root-only exposure of a tree.

The question is simple and direct. Are fruit trees capable of filtering toxins? What are the specifics?

Another website claimed that toxins will settle in the skin of citrus, not the pulp. Is this a folk tale? Let's get some real answers here regarding the tree's ability to filter water from root, to trunk, to branch, to fruit, and what parts of the fruit. In some other plants, leaves are poisonous but fruit or stalk is not, and butterflies also put toxins in their wings. I don't want an answer from a babysitter. I want a concrete answer without concern for whether or not some loon is going to sue you. If you worry about that, quit writing altogether.

Mr. /Ms. kenboe:

First please check the discussion immediatlely preceding your question.

I too find more interesting and helpful information on reading the studies by experts than reading what are more characterized as opinion. Considering the research behind this article and the extensive citations of expert, opinion and scholarly research deserve to be distinguished.

You refer to "your studies" but in fact they are not mine nor any other site editor. Best to take a look at the authors, their qualifications, what they studied and what they concluded. You might also want to take note throughout this article series that we explain the reasoning behind some of the more cautious remarks.

You might want to read in recent work by Leff (2013) who point out that the actual contaminants that are found in fruits and vegetables can vary widely by the particular fruit or vegetable species as well as by growing conditions. So an honest, cogent, informed answer to your "just say yes or no" question, is unfortunately "it depends." That's the real answer, whether it's a comfortable one or not.

For folks who prefer a bottom line and who don't want to read the article itself, an abstract for this article is included in our citations above.

Simple answers may be appealing and you may demand a simple yes or no answer to food crop contamination, but, simplistic answers are often dangerous as well as wrong.

A root crop, ground crop, or tree crop that is perfectly sanitary in a location in one year might be highly contaminated in another year when weather conditions change. Local area flooding, septic drainfield failures, blocked pipes, overflowing septic tanks, a change in septic tank maintenance, even some fool driving a heavy machine over a drainfield so that pipes are crushed or soil is compacted or fill is added, can significantly change where sewage effluent appears and how it affects (or doesn't ) nearby crops.

Risk of drainfield damage from gardening activities

  • some drainfield overgrowth can interfere with transpiration
  • driving garden tractors etc over a drainfield can ruin it

Risk of pathogens entering food crops grown over or near septic drainfields or soakaway beds?

  • the degree to which pathogens may enter food crops grown over a drainfield probably depends on factors such as the crop genera/species, its root properties (depth, length, absorption rate, probably other things I don't know about), and, importantly, the
  • condition of the drainfield as well.

    OPINION: we estimate that a significant portion of onsite wastewater disposal systems are not effectively treating septic effluent well before the property owner recognizes a failure (such as wet areas or odors).

    Particularly this seems the case with some aerobic systems [a high failure rate has been reported, usually due to lack of proper maintenance] and in particular, aerobic septic systems that that use above ground spray to dispose of effluent pose health risks to nearby crops; also cesspools, and septic systems with conventional drainfields in wet or episodically flooded areas are very often not treating wastewater pathogens nor heavy metals.

By no means do we want our content to be inappropriately scary or to give improper guidance about growing crops on or near drainfields; We've had difficulty finding expert authoritative papers and articles on the topic, so we welcome any further comment or citations you can offer.

Bacteriological test suggestions for crops grown close to onsite wastewater systems

For Summer (discussion above), if with all of this arm waving and wailing you want to go ahead with some care, you know some of the worries to attend. It would be useful to actually test some of the produce grown in the vegetable garden you describe for soil & sewage bacteria on both the surface and inside.

It is normal to find bactria in any outdoor soil sample. Your local health department or testing lab can suggest simple procedures for collecting surface and perhaps shallow sub-surface soil or water samples to look for unacceptable levels of pathogens or eColi or other sewage contaminant indicators.

Testing for other potential contaminants such as chemicals that could be present can be more costly and wasteful unless some research suggests specific test targets based on other information about the building occupants, site, nearby sites, history of use of chemicals such as pesticides etc.

4/27/14 Mark said:

How can I get my vegetable and fruit produce professionally tested to ascertain contamination from sewage pathogens?

Reply:

Mark a microbiology test lab, the same folks who do water testing, sewage contamination testing, can test other materials for pathogens. Be sure to discuss with local labs in your area just what is their normal scope of work and expertise. Some labs drastically limit their practice.

To better understand the concerns around pathogens found in fruits & vegetables and how they vary by type of fruit/vegetable as well as growing conditions, I found the following article quite pertinent. Be sure to read the abstract included in our citations even if you don't choose to read the whole article.

  • Leff, Jonathan W., and Noah Fierer. "Bacterial communities associated with the surfaces of fresh fruits and vegetables." PloS one 8, no. 3 (2013): e59310.

My point is that when we ask a lab to test for pathogenic contamination of fruits and vegetables we need to

1. Ignore the folks who argue that such foodstuffs are not at risk and so testing is always unnecessary as well the folks who argue that contamination is so certain that testing is pointless. We are forced by reality to ask the food crop contamination question with more thoughtfulness: what is the crop, where was it grown, when, under what conditions, and exposed to what environment.

2. Ask the microbiology lab what they will test-for, as we might need to look for different pathogens on different foods. I worry that some prior research, as I've found in the area of mold contamination, seriously misreports the presence or absence of hazards because the investigator didn't look thoroughly or used an unreliable test method.

Like bird watching, how do you spot a Quetzal? Well you have to look where they live (in certain areas of Costa Rica) and it helps to know what they eat (little avocados) and when they will be there eating (early morning). Another bird watcher might say there are no Quetzals there, even looking in the same spot, but at the wrong time of day.

Useful Research Citations on Sewage Contamination of Food Crops Grown In or Over Septic Fields

  • Al-Hamaiedeh, H., and M. Bino. "Effect of treated grey water reuse in irrigation on soil and plants." Desalination 256, no. 1 (2010): 115-119.
    Abstract:

    The use of treated grey water (GW) for irrigation in home gardens is becoming increasingly common in Jordan. In this study treated GW produced from 4-barrel and confined trench (CT) treatment units were used for irrigation of olive trees and some vegetable crops. The quality of treated and untreated GW was studied to evaluate the performance of treatment units and the suitability of treated GW for irrigation according to Jordanian standard.

    Effect of treated GW reuse on the properties of soil and irrigated plants at Al-Amer villages, Jordan, has been investigated. The results showed that salinity, sodium adsorption ratio (SAR), and organic content of soil increased as a function of time, therefore leaching of soil with fresh water was highly recommended. The chemical properties of the irrigated olive trees and vegetable crops were not affected, while the biological quality of some vegetable crops was adversely affected.
  • Dar, Imran A., Mithas A. Dar, and K. Sankar. "Nitrate contamination in groundwater of Sopore town and its environs, Kashmir, India." Arabian Journal of Geosciences 3, no. 3 (2010): 267-272.
    Excerpt from abstract: "... The hydrochemical data of 15 samples indicates that the concentration of almost all parameters fall within the permissible limits except nitrate."

    An attempt has been made in this research work to evaluate the concentration of nitrate in groundwater and its management in Apple town and its environs. Groundwater pollution has been reported in many aquifers because of high concentration of nitrate in ground water, which is the result of excessive use of fertilizers to cropland. Systematic sampling was done, with a view to understand the source of nitrate concentration in the study area. Fifteen sample sites were selected and the samples were taken for a baseline study to understand the geochemistry of the study area and to assess its physicochemical characteristics.

    The water quality parameters were investigated for summer (May, 2007) and winter (December, 2007) seasons and were compared with the standard values given by ICMR / WHO. The hydrochemical data of 15 samples indicates that the concentration of almost all parameters fall within the permissible limits except nitrate. Linear Trend Analysis on seasonal and annual basis clearly depicted that nitrate pollution in the study area is increasing significantly. About 85% of samples during summer season and 67% of the samples during winter season were showing a high concentration of nitrate, exceeding permissible limit of WHO (50 mg/l), which is due to the use of nitrogenous fertilizers in the study area. Appropriate methods for improving the water quality and its management in the affected areas have been suggested.


    تلوث المياه الجوفية بالنترات في مدينة سوبور ومحيطها بمقاطعة بارامولا كشمير – الهنديهدف هذا البحث إلى تقييم تركيز النترات في المياه الأرضية وإدارتها في مدينة سوبور ومحيطها. قد لوحظ تلوث المياه الجوفية في كثير من الخزانات الجوفية نتيجة للتركيز العالي للنترات في المياه الأرضية وذلك للاستخدام الجائر للأسمدة في زراعة المحاصيل الزراعية.في هذا الخصوص تم تصميم منهجية أخذ العينات بغرض تحديد مصدر النترات بمنطقة الدراسة. و تم أخذ 15 عينة لدراسة وللتعرف على الكيمياء الأرضية بمنطقة الدراسة وتحليل الخواص الكيميائية الطبيعية. تم فحص عناصر جودة المياه لصيف 2007 (شهر مايو) وشتاء 2007 (شهر ديسمبر) وتم مقارنتهم بالمعايير الخاصة ب ICMR/WHO ودلت البيانات الهيدروكيميائية للـ 15 عينة أن جميع المعاملات تقع في الحدود المسموح بها ماعدا النترات. ودلت نتائج التحليل الخطى على المستوى الفصلي والسنوي أن تلوث النترات يزداد بدرجة ملحوظة. كما دلت 85% من عينات الصيف و 65% من عينات الشتاء على تركيزات عالية للنترات تفوق الحدود المسموح بها من ICMR/WHO (50 مليجرام/لتر)، وقد يُعزى ذلك إلى استخدام المسمدات النيتروجينية. وقد تم اقتراح طرق مناسبة لتحسين نوعية المياه وإدارتها بمنطقة الدراسة.
  • Heinonen-Tanski, Helvi, and Christine van Wijk-Sijbesma. "Human excreta for plant production." Bioresource technology 96, no. 4 (2005): 403-411.
    This study explores use of human excreta as a natural resource for agriculture.
  • Heukelekian, H. "Utilization of sewage for crop irrigation in Israel." Sewage and Industrial Wastes (1957): 868-874.
    The authors argue that

    Failures and difficulties with the disposal of sewage by crop irrigation need not arise when utilization is the main objective. The natural tendency with land disposal of sewage is to apply as much sewage as possible in a limited area at rates higher than can percolate through the soil. Waterlogging of the soil and odors are the common result of such practice. The anaerobic condition which may result is known as "soil sickness".

    On the other hand, when the application of sewage to the land is geared to the needs of the soil and the crop, odor and waterlogging difficulties do not arise. There are a number of examples all over the world of successful utilization of sewage for crop irrigation.


    The aricle continues to point out important variables including the level of rainfall, even when sewage application rate is controlled to be suitable for crops.
  • Illinois Windbreak Manual, A. Field. "Illinois." (1990). [PDF] - http://web.extension.illinois.edu/forestry/iwm_complete.pdf
  • Leff, Jonathan W., and Noah Fierer. "Bacterial communities associated with the surfaces of fresh fruits and vegetables." PloS one 8, no. 3 (2013): e59310.
  • Abstract:

    Fresh fruits and vegetables can harbor large and diverse populations of bacteria. However, most of the work on produce-associated bacteria has focused on a relatively small number of pathogenic bacteria and, as a result, we know far less about the overall diversity and composition of those bacterial communities found on produce and how the structure of these communities varies across produce types.

    Moreover, we lack a comprehensive view of the potential effects of differing farming practices on the bacterial communities to which consumers are exposed. We addressed these knowledge gaps by assessing bacterial community structure on conventional and organic analogs of eleven store-bought produce types using a culture-independent approach, 16 S rRNA gene pyrosequencing.

    Our results demonstrated that the fruits and vegetables harbored diverse bacterial communities, and the communities on each produce type were significantly distinct from one another. However, certain produce types (i.e., sprouts, spinach, lettuce, tomatoes, peppers, and strawberries) tended to share more similar communities as they all had high relative abundances of taxa belonging to the family Enterobacteriaceae when compared to the other produce types (i.e., apples, peaches, grapes, and mushrooms) which were dominated by taxa belonging to the Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria phyla.
    Although potentially driven by factors other than farming practice, we also observed significant differences in community composition between conventional and organic analogs within produce types. These differences were often attributable to distinctions in the relative abundances of Enterobacteriaceae taxa, which were generally less abundant in organically-grown produce.
    Taken together, our results suggest that humans are exposed to substantially different bacteria depending on the types of fresh produce they consume with differences between conventionally and organically farmed varieties contributing to this variation.
  • Mara, Duncan. "Sanitation: What's the Real Problem?." IDS Bulletin 43, no. 2 (2012): 86-92.
    Abstract:
    The vast number of people without sanitation raises the question why this is so. It cannot be a lack of adequate sanitation technologies as these exist for all situations from dispersed rural communities to high-density low-income urban areas. Nor cannot it be money as development banks will readily fund a well-prepared sanitation proposal. The real sanitation problem must surely lie with those developing-country governments who have shown little commitment in practice to sanitation despite international sanitation advocacy since 1980. Their lack of commitment is clearly shown in the number of ‘open defecators’ in the world today. There are fortunately some countries that have done well: Malaysia, Thailand and Vietnam, for example, but they are a clear minority.
  • Mogheir, Y., T. Abu Hujair, Z. Zomlot, A. Ahmed, and D. Fatta. "Treated Wastewater Reuse in Palestine." In International conference Water Value and Rights, Ramallah-Al-Bireh, Palestine May. 2005.
    Abstract:

    Treated wastewater resource is an environmental, social and economical good that needs to be managed in appropriate way. Palestinian Territories, as in most of the neighboring countries in the Middle East region, acknowledges the importance of this resource in improving the water deficit by reusing the treated wastewater in agricultural production, industrial sector and recharges the aquifer.

    However, this resource is strictly sensitive and has adverse impacts on the public health. Both negative and positive impacts of the treated wastewater resource should be considered. Therefore, Environment Quality Authority (EQA) has prepared Environmental Law and Standards Draft for reusing the treated wastewater.

    Moreover, Palestinian Water Authority (PWA) prepared a National Water Plan where the treated wastewater reuse has an essential part. EQA is currently sharing a project which considers the development of tools and guidelines for the promotion of the sustainable urban wastewater treatment and reuse in the agricultural production in the Mediterranean countries. This paper presents the Palestinian practices and plans in wastewater treatment and reuse.
  • Nair, Jaya. "Wastewater garden--a system to treat wastewater with environmental benefits to community." Water Science & Technology 58, no. 2 (2008).
    Abstract:

    Many communities and villages around the world face serious problems with lack of sanitation especially in disposing of the wastewater--black water and grey water from the houses, or wash outs from animal rearing sheds. Across the world diverting wastewater to the surroundings or to the public spaces are not uncommon.

    This is responsible for contaminating drinking water sources causing health risks and environmental degradation as they become the breeding grounds of mosquitoes and pathogens.

    Lack of collection and treatment facilities or broken down sewage systems noticed throughout the developing world are associated with this situation. Diverting the wastewater to trees and vegetable gardens was historically a common practice. However the modern world has an array of problems associated with such disposal such as generation of large quantity of wastewater, unavailability of space for onsite disposal or treatment and increase in population.

    This paper considers the wastewater garden as a means for wastewater treatment and to improve the vegetation and biodiversity of rural areas. This can also be implemented in urban areas in association with parks and open spaces. This also highlights environmental safety in relation to the nutrient, pathogen and heavy metal content of the wastewater. The possibilities of different types of integration and technology that can be adopted for wastewater gardens are also discussed.
  • Nelson, M., F. Cattin, M. Rajendran, and L. Hafouda. "Value-Adding through Creation of High Diversity Gardens and Ecospaces in Subsurface Flow Constructed Wetlands: Case Studies in Algeria and Australia of Wastewater Gardens Systems." In Proceedings of 11th International Conference on Wetland Systems for Water Pollution Control, edited by S. Billore, P. Dass, and J. Vymazal, vol. 1, pp. 344-356. Ujjain, India: Institute of Environmental Management and Plant Sciences, Vikram University, 2008.
  • Sipahioglu, H. M., A. Myrta, N. Abou‐Ghanem, B. Terlizzi, and V. Savino. "Sanitary status of stone‐fruit trees in East Anatolia (Turkey) with particular reference to apricot." EPPO Bulletin 29, no. 4 (1999): 439-442.
    Abstract:

    Field surveys were carried out in the main stone-fruit-growing areas of East Anatolia (Turkey) to assess the sanitary status of varietal collections, mother blocks and commercial orchards. The presence of virus and virus-like diseases was ascertained by enzyme-linked immunosorbent assay (ELISA), sap transmission to herbaceous hosts, graft transmission to peach cv. GF305 and molecular hybridization tests.

    A total of 1019 samples was tested by ELISA (859 apricot, 120 cherry, 21 almond and 19 peach). The sanitary status of apricot was extremely satisfactory, as the infection level was less than 0.3%. Cherry and almond, however, showed 21% and 33% infection respectively. The viruses identified were apple chlorotic leaf spot trichovirus (ACLSV), prune dwarf ilarvirus (PDV) and prunus necrotic ringspot ilarvirus (PNRSV).

    The commonest virus was PDV. Plum pox potyvirus (PPV), apple mosaic ilarvirus (ApMV) and the nepoviruses tomato black ring (TBRV), raspberry ringspot (RpRSV), strawberry latent ringspot (SLRV), cherry leaf roll (CLRV), arabis mosaic (ArMV) and tomato ringspot (ToRSV) were not encountered. Peach latent mosaic viroid (PLMVd) and hop stunt viroid (HSVd) were not detected either.
  • Watson, John Lionel Airay. "OXIDATION PONDS AND USE OF EFFLUENT IN ISRAEL." In ICE Proceedings, vol. 22, no. 1, pp. 21-40. Thomas Telford, 1962.
    Excerpt from abstract:

    The evolution of sewage treatment in oxidation ponds in Israel overthe past decade is described. The high degree of purification is shown to be due to the work of algae, of which Chlorella is the most prolific. The photo-synthetic action of light and the heat that it generates build new algal cell material...

 

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