As a descendant of the Rodale tradition of compost = garden gold, it can be hard for me to learn that not all compost and not all manures are good.  Some can even be toxic and kill your garden.

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National Gardening Association  Clopyralid (herbicide), used in lawn care, has shown up as a contaminant in composting facilities from Pennsylvania to Washington.Clopyralid-contaminated compost can be toxic to sunflowers, peas, beans, tomatoes, and potatoes....  clopyralid doesn't break down under normal composting processes, and it can be a hazard to these plants even at low concentrations.

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grist.org  California regulators traced residues of dichlorophenyl-dichloroethylene, a breakdown product of DDT, and bifenthrin, an ant killer, to compost in pots of organic wheatgrass ...DDT was banned for most uses in the early ’70s and bifenthrin is classified as a possible human carcinogen and is highly toxic to fish. The NOP initially proposed setting a strict upper limit for bifenthrin levels in compost but abandoned the idea when wider tests revealed that many brands of commercial compost wouldn’t pass. Regulators ultimately decided to allow any level of contamination in compost so long as “residual pesticide levels do not contribute to the contamination of crops, soil, or water.”

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Rodale.com " avoid compost that lists "biosolids" as an ingredient—... word for human sewage sludge." and grist.org " sewage sludge...basically anything that gets washed down the drain...heavy metals...pesticides...pharmaceuticals (lots of Prozac, antibiotics, and birth-control-pill hormones), flame retardants...dioxin. "

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MotherJones.com  "Kellog" brand compost, supposedly "organic" is made with Sewage Sludge.  

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SanFrancisco was apparently giving away compost to gardeners...  which contained toxic sewage sludge.  

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Terrible story from the UK.  Dow produced herbicide that was used for crops that were fed to cattle.  The cattle manure was sold to gardeners.  The herbicide damaged garden vegetables and ruined the soil.  

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MotherEarthNews.com    clopyralid and its close cousin, aminopyralid, easily persist, sometimes for YEARS!, in hay, manure and compost....used in food gardens, tomatoes, beans and other sensitive crops develop curled foliage that looks like a disease, if they grow at all.   alsoDow herbicides in composts.

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Ohio State University Extension.    "as little as 2 parts per million (ppm) of 2,4-D (Weed-B-Gone) or 50 parts per billion of Clopyralid significantly reduce the growth of sensitive plants like tomato" although they report most pesticides degrade rapidly.  also clopyralid is very persistent in composts and manures and is largely unaffected by the composting process. Most plants are not damaged by clopyralid, even at rates used on lawns and agricultural crops. However, plants in the bean family (Leguminosae), the potato/tomato family (Solonaceae), and the sunflower family (Compositae) are very sensitive to this herbicide. It can stunt tomato, clover, lettuce, pea, lentil, sunflower, pepper, and bean plants at levels in compost as low as 10 parts per BILLION! Since the level of clopyralid on grass the day of application is 10,000 to 50,000 ppb, even a small amount of contaminated material entering a composting facility or directly applied to sensitive crops can cause major problems.

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In WA State:  big losses for some gardeners.

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Looks like Clopyralid is banned, but as a home product may continue to show up in city yard-waste compost as chemical-using homeowners use up their supplies.  Then, of course, there is always the next product on the market, and no one will know until there is another disaster.

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I couldn't find a list of garden products containing biosolids (sewage sludge compost).  Apparently in WA State there is "GroCo".  Apparently it's tested for a variety of contaminants.

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None of this is meant to scare anyone off from using commercial composts or manures.  I've been using local yard debris compost to enrich my garden for over a decade.  Lately I've been mixing it into my new raised beds, adding about 25% to the otherwise poor topsoil.  It makes a big difference in fertility, drainage, workability, soil texture, and plant growth.   I've been to the composting center - they have big mountains of compost.  I hope any contaminants are well diluted and most are degraded.  Without the compost, my garden would be much less productive and fertile.  Still, whenever possible I'm using my own leaves, grass, chicken manure, etc.  I do think it's important to know what we are doing, and be aware there is potential harm in something we think is universally good.