Sunday Commentary: Do We Gain Anything from Additional Air Quality Study of Nishi?

Critics of the Nishi project continue to raise the question of, if there are no problems with the Nishi site, why not just do the studies that Dr. Thomas Cahill is asking for?  But the question I keep asking – to which there has been no satisfactory answer regarding the limited duration of residencies at Nishi – is what level would have to be present in order to create a problem?

That would seem to be a fundamental question.  Because, despite claims by Thomas Cahill that this is one of the most polluted sites in the nation, clearly the data we have doesn’t suggest a huge health threat.

How do we know that?  Because the Draft EIR references the work done already to sample air quality at a location that was near and not on the actual site.  Critics have complained that those findings are problematic because the 10-day measurement wasn’t representative of the possible range of conditions and, again, wasn’t performed on the site.

The EIR notes that “the concentration of diesel PM on the Nishi site approximately 300 feet from the edge of I-80 was estimated to be approximately 0.57 micrograms per cubic meter (μg/m3). This estimate is based on the particulate measurements conducted near the Nishi site in February 2015.”

So, while clearly neither Dr. Cahill nor other critics believe that level of exposure is above the critical level, they also have yet to define what the critical level is for a few years of exposure and, until and unless they do that, any attempt to further study Nishi is akin to hitting a moving target.

In his op-ed this week, Thomas Cahill continues to raise issues that Nishi is one of the most polluted sites in the nation.

But there are reasons to be skeptical of these claims.  Data compiled over a 10-year period suggests wind patterns would not produce the worst case scenario most of the time, and a question that I
continue to ask is how high do the particulate matter levels have to be in order to actually cause problems over such a limited exposure time?

They base risk levels to a 70-year exposure, but most people at the proposed Nishi site will live there for one year, with a possibility of two to three years at most.

The other problem is that reaching Dr. Cahill’s threshold appears to be akin to hitting a moving target.

In an email exchange a decade ago, Dr. Cahill told Tim Ruff the “bad news” about conditions at a huge rail freight station.  But Nishi isn’t building by a huge freight station, which would be worse “because the engines are left idling.”

Then Dr. Cahill writes that “it is the 24 hr/day factor that drives the bad news for residences, and most of that is indoor. It is possible with very minor modifications of heating/cooling systems to make the air inside the houses essentially pristine. We did such tests as part of the vegetation study, and in a test, reduced diesel/smoking car exhaust in Arden Middle school by 70%.”

Moreover, in a 2007 study that Dr. Cahill was a part of, they found that “vegetation near very fine particle sources can be effective in removing some of the most toxic particles in the air before they get mixed into the regional air mass.”

The opponents and critics of Nishi keep calling for more testing on the site.  But is testing really going to resolve the problems?

For example, Charles Salocks in analyzing 10-year wind direction data, found, “Worst case scenario winds (SW) occur very infrequently (5% of the time).”

Second, toward my question about exposure time, “The health assessment in the EIR is based on an assumption of a residency of 70 years with no mitigations. (The) typical residency at Nishi will be 1-3 years, not 70. This alone reduces long-term health risk by at least 95%.”

He also found that the mitigations will further reduce exposure.

“A 100’ x 2000’ peripheral greenbelt and an internal ‘urban forest’ will filter particulates from the freeway.  Future residents of Solano Park, and other nearby properties, will also benefit from this measure.  Air filtration systems will further enhance indoor air quality where students spend most of their time,” the professor wrote.

Then there was the presentation by Don Shor.  He found that the urban trees play a huge role in reducing pollution and improving air quality by as much as 16 percent.

Among the studies cited:

  • Trees planted outside the home can provide substantial reductions in PM inside the home (>50% reduction).
  • A field study in Sydney, Australia, showed a 42% reduction in particulate matter from sites with more trees.
  • Cahill (2008) found that redwood vegetation removed 79% of 0.17μm diameter particulate matter in a wind tunnel experiment.
  • Further wind tunnel research used by Dr. Cahill estimated very high filtration of very fine particles by two species of conifers (redwood and deodar cedar), from 79 – 99%.
  • As of April 2017 the state Air Resources Board now includes vegetative buffers among their recommended strategies that reduce traffic emissions.

So what we have now is a growing body of counter-evidence.  Data on the wind directions suggest that the worst case scenario only happens 5 percent of the time – we have ten-year wind studies that won’t be impacted by more on-site study.

We have research on mitigation measures such as air filtration.  Once again, additional on-site studies will not better inform that.  A decade ago Dr. Cahill said filtration units could reduce particulate by matter by 70 percent, and the EIR with more modern techniques has pushed that higher.

We have research on the impact of vegetation – including a decade-old study from Dr. Cahill himself that concluded: “[V]egetation near very fine particle sources can be effective in removing some of the most toxic particles in the air before they get mixed into the regional air mass.”

If that is the case, then we won’t know what level of particulate matter actually reaches the residents until and unless the site is built and tests are done then.

Finally, as Dr. Salocks has pointed out, echoing our point, the health assessment is based on a 70-year residency assumption, and, if the typical residency at Nishi is more like one to three years, that alone will reduce any long-term health risk by a huge amount.

If all that is true, how is air quality testing going to help us answer the problem any more than we have it right now?  The mitigation measures, the vegetation, the wind directions and the exposure time are all crucial variables and none of them will be better informed by more testing on-site.

So my question remains, what do we actually gain by doing further studies?  Is this just a delay tactic by opponents of the project?   Can we establish a level of danger prior to additional study?

A telling answer from Dr. Cahill may explain his view, though, and whose view seems captured here: “Even one preventable death is not acceptable.”

His allowable risk level is therefore not merely very low, but zero.  If that is the case, why bother with further air quality studies – he already has his answer.  The risk isn’t zero, it’s just very low and it can be mitigated.

Until someone wants to define what the acceptable risk is, there is no point to any further study.

—David M. Greenwald reporting

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About The Author

David Greenwald is the founder, editor, and executive director of the Davis Vanguard. He founded the Vanguard in 2006. David Greenwald moved to Davis in 1996 to attend Graduate School at UC Davis in Political Science. He lives in South Davis with his wife Cecilia Escamilla Greenwald and three children.

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  1. Ron

    From article:  “The opponents and critics of Nishi keep calling for more testing on the site.”

    Factually untrue.  There has been no testing conducted on the site.

    1. Howard P

      Au contraire, mon frere, depending on parsing.  And a tiny comma…

      Try, “The opponents and critics of Nishi keep calling for more testing, on the site”.  Testing was done in the near vicinity.

      1. Ron

        The way that David has worded this implies that testing was already done on the site.  That is not accurate.

        By the way, why wasn’t testing done on the site, itself (instead of “nearby”)?  Was permission to do so withheld? If so, why?

        1. Howard P

          Ask Cahill and the owners… was permission requested?  And if not, why not? [BTW]

          The way that David has worded this implies that testing was already done on the site.  That is not accurate.

          For the lack of a comma?  Next will be misspellings and grammar… but David is in the best position to answer about what he wrote, and his intent.  I don’t know…

        2. David Greenwald

          My intention was to say that there has been a push to do additional testing, on the site.  Refer to paragraph three where I quote from the EIR (in paragraph 4) and make it clear that a complaint with previous testing was that it was not done on site.  That should clarify the intent of the sentence in question.

        3. Howard P

          And, by the plain meaning of your words, Ron, you have “implied” that David wrote an untruth… twice.

          Factually untrue.

          Your words.  Saying David wrote an ‘untruth’.  Then ‘back-pedalling a bit,

          The way that David has worded this implies that testing was already done on the site.  That is not accurate.



      2. Ken A

        I read that the testing was done at the end of Olive “near Nishi” in an area surrounded by a body shop, a small engine repair shop, a smog check place and multiple other auto related business.  I don’t have any degree related to testing air, but every time I stop by JBs at the end of Olive to have work done on my chainsaw, lawn mower or weed whacker I can smell the two stroke oil in the air.  Since I’m not an expert on testing the air quality of vacant farm land I  would be interested to hear the “technical” reason that they decided to test the air quality at the end of a street with the highest concentration of auto/paint/engine related business in the city rather than test the air quality at the center of the ~40 acre vacant parcel.

  2. Don Shor

    I visited the property and nearby areas with Tim Ruff to determine the most feasible and appropriate site location. We had had several preliminary conversations primarily dealing with the logistics required of a site, but also discussed potential locations on and adjacent to the Nishi property. We visited the area and determined a location immediately east of the property, near Olive Drive would provide the facilitation necessary for siting. Although the Olive Drive site (OlDr) location was not on the property, the position with respect to the freeway was analogous to the middle of the property and therefore should provide comparable results….

    Full report here.


    1. Tia Will


      I apologize because I realize that you and others may have addressed this previously, but I am confused. While I did not re read the full report, I did read the portion on site selection. While it is stated that, “the position with respect to the freeway was analogous to the middle of the property and therefore should provide comparable results….”. 

      However, while the similar position with respect to the freeway was adjusted for, I did not see any mention of how the other businesses in the area with their byproducts ( frequently sufficient to produce a noticeable smell) might change the results. Was this also corrected for, or just not mentioned in the complete report ?


  3. David Greenwald

    Also interesting to note, that Ron asked whose decision it was to test off-site.  Answer: Thomas Cahill.

    ”Cahill chose the site for the study.  He needed electrical power and he needed a secure location and it was placed on the roof at a location chosen by Barnes, his associate, as representative of conditions at Nishi.   And it cost $16,000.”

    1. Ron

      David:  Thanks for the clarification.  I understand the situation better, now.

      There was a study that was intended to be preliminary, and not fully funded.  (Hence, the choice was made to find a location that fit within those parameters, for both security and access to electricity.)  Based upon the negative, preliminary results, Dr. Cahill recommended that a study be conducted on the site, itself.

      And, the actual selection of the off-site location was made by Dr. Barnes.

        1. David Greenwald

          “Although the Olive Drive site (OlDr) location was not on the property, the position with respect to the freeway was analogous to the middle of the property and therefore should provide comparable results….”

        2. Ron

          My first time actually seeing this report, but this is from the first page:

          “One goal of this study was to provide measurements and analysis on a short
          time frame.”

          Again, negative preliminary results were already received.  Hence, the recommendation for a study that does not have the financial and logistical limitations of the preliminary study.

          But, thanks for filling me in.  You and Don are clearly more interested in this, than I am.  (But, it seems like it’s for the purpose of downplaying the preliminary results.)


          1. David Greenwald

            If you believed that the existing results discredited the project, you wouldn’t be pushing for additional study.

        3. Howard P


          Hence, the recommendation for a study that does not have the financial and logistical limitations of the preliminary study.

          Equals blank check from someone?  Ten-fifteen year study to assure variables are addressed?  Not happening…

          My bad… you said ‘logistical’… others will raise “statistical” issues…

        4. Ron

          David:  I’m not sure what to think regarding the preliminary results, or the effectiveness of Don’s redwood trees.  Again, I haven’t been following this issue that closely, partly because it is very technical in nature.  And, partly because there is no participatory debate from the experts regarding this subject.  (Mostly, it’s just you and Don hammering away at it, day-after-day.  Aided by a chorus of those who clearly support the proposal, regardless of air quality.)

          But, we do know that Dr. Cahill has submitted articles, which clearly raise concerns. Some of which appears to be new information, regarding the risks. To my knowledge, Dr. Cahill has no other “agenda”.

          And, we know that the preliminary study had already indicated negative results.

        5. David Greenwald

          Ron: I wonder if you even bothered to read this article.  You made a false accusation against me earlier, didn’t apologize when you were shown to be wrong, and you haven’t responded to anything in this article other than a single line that I could have been more clear with (but whose meaning would have been obvious had you read paragraphs 3 and 4).

        6. Ron

          David:  Look at the title of your article, and you’ll see that it (also) has the same misleading wording.  And, just last night we were going over this same exact point, in the comments from the other article regarding Nishi.

          What I’m really objecting to is the daily onslaught of one-sided information, whether it’s air quality, fiscal impacts, or other issues.  It’s misleading.

        7. Ron

          I would add that repeatedly presenting one-sided information actually ends up hurting an argument, as credibility is diminished.  Ultimately, the only ones you’re going to “convince” are those who are already part of your choir.

          On the “positive” side, at least you’ll end up further alienating those you’re opposing.  Maybe that’s the way to “win” in politics, these days.

        8. Ron

          If you actually took the time to present balanced articles, you might have a better shot at bringing people together, instead of driving them apart.

          I, for one, do not like to see issues such as air quality used as a “political tool”, by those who are for, or against a proposal.  However, you’re the one with the daily blog (and daily onslaught of one-sided propaganda).

          Those who simply ignore it (rather than responding) are probably the wisest of all.

  4. Todd Edelman

    This project could be considerably more… pleasant if we were more serious about challenging the false uncontrollable reality of the I-80’s toxic onslaught on our city. I’m talking not only about gases and particles but vibrations – sound – and not only objectivity but subjectivity: It’s simply a loud location outside or with open windows, and “I’m busy now trying to do my work and get out of here in a couple of years. Please leave a message” is hardly the most nurturing outgoing message for voice mail.

    I’m not throwing around random idealistic verbiage with the goal of blocking the project. For months in this space I’ve suggested ideas for truly containing the sound issues. And with Sterling I was the one who said that there could even be more housing than planned if most private car parking was removed from the scenario… and that a bicycle connection via Pole Line and Olive would be a great one to campus.

    To rephrase part of my comments from Thursday’s article: It’s frustrating this repeated figure of 5% – its source the analysis by Dr. Salocks – as 60% of the time the wind blows from the south – from the I-80. It’s only the higher polluting transition area of the I-80 that’s southwest of the project.

    I also mentioned in comments on last Thursday’s article:

    The I-80 is located to the south and southeast of Nishi, and I am curious if the winds here are really so similar to those at the airport, though the two locations are only a bit less than two miles apart. The airport is in an open area and the I-80 is the south and southeast of a built-up area that generates and retains heat relative to the surroundings, and doesn’t heat draw in air from cooler areas? Perhaps significantly, how does wind direction relate to time of day? What if a sort of chronic “worst case scenario” is that at peak travel times the wind comes from the southwest and south? (To be fair this could be even better if during peaks the wind comes from the north.) I am also not clear if there were any trends present in that ten-year profile.

    And also:

    “The project is said to have risks to residents, but these are meant to mitigated by the nature of short term residency of most who will live here.  The problem here is that this ignores the possibility – if not likelihood – that these short term residents will live in other polluted areas in the future, or, of course, that they have lived in polluted areas in the past. Some come from Los Angeles, others from Mexico City, others from Beijing. Going forward, it reduces their opportunities to stay healthy in other polluted places, and – if they are concerned about their own health – it lowers their future housing opportunities. Nishi – at best – creates short term problems for people who will have other short term problems in the future.”

  5. Jeff M

    Only in Davis would the opponents of any and all peripheral development get to recycle fake health risk “science” that gins up irrational fear in our community of organic granola crunchers.

    1. Tia Will


      Not so. There are many communities in which it is just as easy to stir up fear amongst soggy cereal slurpers by citing false health risks. I remember one instance of someone claiming in public that doctors, including pediatricians, in favor of a public health measure were “trying to poison children”. Sound familiar ?

  6. Alan Miller

    “Even one preventable death is not acceptable.”

    Does Cahill and his minions feel the same about driving?  Flying?  Bicycling? Riding a train?

    Guess we ain’t going anywhere.

    Don your rubber bubbles!

  7. Tia Will


    I would like to direct you again to the Title of this submission, “Sunday Commentary….”

    I believe that you are choosing not to differentiate between news articles, in which I would hope, unless it is essentially an unaltered press release, consistently stated on the Vanguard, and commentary or opinion pieces. In news articles, I would anticipate that there would be some acknowledgement/ balancing of alternative points of view. In commentary or opinion pieces, I see no need as they are clearly delineated as the author’s opinion. I feel that this was a genuine issue on the Vanguard several years ago, which has been largely ameliorated by David’s clarification of what is news vs what is opinion, usually in his title.

    1. Ron

      Tia:  One’s choice of “news” articles is often influenced by one’s “commentary”.

      Regarding debate of the actual issues – that’s quite often lacking, on the Vanguard.  For example, I’ve suggested that David reach out to Ray Salomon, regarding his fiscal analysis.  Unfortunately, that has (apparently) not occurred.

      Regarding air quality, Dr. Cahill would probably be the one who is most qualified to debate the research.  Perhaps he chooses not to, on a blog that allows personal attacks.  (Witness the personal attacks made about Dr. Cahill, in his article from a couple of days ago.)

      It should be noted that David and Don don’t actually conduct “research” per se, but simply present arguments (apparently with a goal of supporting particular development proposals).

      I have seen others (e.g., Roberta) debate these issues, but perhaps she’s grown weary of attacks (and repetitive arguments), as well.  Not sure. (In any case, her background/expertise is also apparently not in air quality.)

      1. Richard McCann


        I have expertise in conducting economic analyses on air quality and regulation. While Dr. Cahill may be better qualified on conducting analyses on the chemical composition of the pollutants, our expertise overlaps on risk assessment, and I have more expertise on valuation and policy implications related to air quality issues.

        As for the repetitiveness of the arguments, this may appear to be so because the same points keep being brought up over and over by the opponents, and they fail to update their analyses for the valid points raised by those arguing against them. So of course it looks repetitive. If they want the debate to move forward, they need to develop a point by point rebuttal to the issues raised. I haven’t seen that yet.

  8. Richard McCann

    That winds blow out of the SW are not a problem–they are often accompanied by atmospheric conditions that dissipate/mitigate any pollution (can you say “rain”, as one example?) But more notably, as I posted a couple of months ago, looking at the monthly wind rose shows that the during the school year, the least damaging weather conditions exist. During the summer when the student population will be greatly diminished (does anyone have data on West Campus housing rates by month?) is when the north winds blow that might bring in locomotive emissions, and the worst of the southwest winds in hot conditions blow. There is a real lack of

    As for absolute safety, Alan Miller made a good point about how Cahill is ignoring all of the other mortality risks he creates in his personal day to day life. Hypocrisy is the worst of crimes. Or maybe it just illustrates his ignorance.

    As for a policy stance, the common valuation for an increased safety risk is about $10 million per statistical life. This valuation holds across a number of regulatory forums, and reflects a societal consensus. Individuals may think otherwise, but we are a representative democracy and individuals do not set the rules if we can help it.

    1. Howard P

      Richard… you should have saved your breath and post (as, I’m realizing, should have I).  Most who are familiar with the sciences are “already there”…. those who aren’t, will never be convinced, and many (not all) of them have “agendas” other than air quality, mortality, and morbidity.

      For those who don’t (the ones with the other agendas, and maybe one or two zealots on the concept that ‘nothing bad should ever happen to anyone at any time’) fifteen years of testing at 40 sites within Nishi, will poke holes.  Even if they were brought to the table to define the scope of such studies…

      Just my informed opinion…

    2. David Greenwald

      Richard: Speaking of mortality risks, which is higher – the risks of additional driving two and from campus over a three period or the risks of particulate matter exposure at Nishi over the same time period?

      1. Howard P

        David… I think, you, Richard and I are on the same page here… no credible threat, and as you point out, except for the “do nothing”option, better than alternatives FOR THE SITE.

        1. Howard P

          Also, let’s be real… there are already ‘residents’ on the Nishi site (or, on the immediate borders thereof)… the homeless.

          Many have lived there for 3- years…

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