Assessing the Nature and Severity of the Health Risks at Nishi


Much of the concern about the air quality issues at Nishi focus around the work of Thomas Cahill, a respected Professor Emeritus and an expert on air quality.  For at least the last year and a half he has expressed concerns about “the viability of the Nishi property for residential use.”

In short, he argues that Nishi is directly downwind from I-80 with a number of air quality factors, and in close proximity to a heavily-trafficked rail line as well.  He argues, “These aerosols are closely tied to decreased lung function in children living near Los Angeles freeways and a greatly enhanced death rate from heart attacks in the southern San Joaquin Valley (and to a lesser extent in Sacramento).”

He argues, “These reasons form the basis of my opposition to single family or condominium residential use that would expose sensitive populations, especially children and the elderly, to the diesel exhaust and the ultra-fine metals from 1-80 vehicles, especially during braking.”

At the same time, in his 2015 letter responding to the EIR, he suggested that he is in favor of urban infill “as a way to address Greenhouse Gas emissions and climate change.”  As such, he recommends a two-year study period for the aerosols at the Nishi property, he proposes an “apartment dwelling proposed use (of) the technique of low pressure drop ultra-filtration,” and suggested that, prior to residential use, “the buildings be evaluated for effectiveness of the mitigation efforts, and modifications made if necessary to improve air quality to at least City of Davis average in-home values as measured near City Hall.”

Dr. Cahill told the Vanguard in an email that “the regulations have fallen way behind the medical and air quality research, and do not take into account the stunning advances of the past 15 years.”  He would add that “a group of 30 health and environmental scientists” that he works with argue that “existing regulations do not protect people within 1,000 ft of freeways where braking and acceleration occur, and especially downwind of an elevated section.”

Tim Ruff, the project manager for Nishi, told the Vanguard that the development team met with Professor Cahill and on the basis of his concerns “changed our plans years ago.”

“He said single family type units each with separate entrances and exits and yards was not a good plan,” Mr. Ruff told the Vanguard in an email.  “He suggested 5-6 story residential buildings where indoor air quality could be better controlled and centralized.  We made that change and put the for sale as far away as possible. The plan before the voters is the Tom Cahill plan.”

As Mr. Ruff notes, the EIR consultants spent quite a bit of time responding to the concerns of Professor Cahill in their analysis.  To address the air quality issue the project has adopted an air filtration system, along the lines suggested by Dr. Cahill, “The air filtration systems on all residential buildings and buildings in which people work shall achieve a minimal removal efficiency of 95 percent for UFP (particulate matter with an aerodynamic diameter of 0.1 microns and smaller).”  These measures including pressuring buildings, double-door entrances, and a high-volume, low-pressure drop air exchange system.

One of the big questions that arises is not whether exposure to these particulate matter is harmful to the health of residents, but how to place that within and overall risk assessment.

Page 62 of the final EIR explains that the consultants compared air pollution health risks within other areas of the state.  They write, “South Coast Air Quality Management District (SCAQMD) conducted a district-wide evaluation of air pollution health risks in 2014, finalized in May 2015. The average air pollution health risk was estimated to be 1,025 per 1,000,000 residents (SCAQMD 2015). The report also estimates that diesel particulate matter represents approximately 80 percent of the total air pollution health risk or 820 per 1,000,000 residents.”

Here they find that the DPM (Diesel Particulate Matter) health risk, in the unmitigated form, “at the Nishi site was determined to be approximately one-fourth of that.”

They add, “The Sacramento Metropolitan Air Quality Management District (SMAQMD) estimates that the reasonable worst-case level of health risk from free-way generated toxic air contaminants is approximately 919 per 1,000,000 residents for a residential dwelling located just 50 feet from the busiest freeway in Sacramento County.”

Gary Jakobs, the EIR consultant, told the Vanguard that “a health risk, as presented in the Nishi EIR, is most easily and readily defined as the possibility or estimated probability of adverse health effects (e.g., illness, injury, or disease) from a person’s exposure to toxic air pollutants. The numbers presented in the EIR are a quantitative measure of the probability of such a risk.”

He noted, “A health risk is not a guarantee that a specific number will contract a particular adverse health effect, but rather an assessment of a particular condition (e.g. proximity to elevated freeway) and the probability that individuals subject to that condition could experience an adverse health effect.”

“It is true that the conditions at the Nishi site do not make it the worst place to live in the state,” Mr. Jakobs stated, adding that “the relative health risks within many of the urban areas in the state are likely much greater.”

He also stated, “It is important to note that ultra-fine particulates (UFP) is not generally assessed as part of current health risk assessments, and there are no established ambient air quality standards (national or state) for UFP, as of yet.”

Back in January, Mayor Pro Tem Robb Davis, himself a public health professional, argued that the risk assessment at Nishi was actually quite low.

Section 4.3 of the Draft EIR for example, notes, “One common metric of health risk is the number of additional cancer cases that may occur in the population exposed to a particular TAC [toxic air contaminant], or located in an area exposed to TACs in general. This is typically reported as additional cancer risk per million people.”

Here the EIR notes that, according to the American Cancer Society, “the lifetime probability of contracting/dying from cancer in the United States is 43.3%/22.8% among males and 37.8%/19.3% among females.  In other words there is a lifetime probability that over 430,000 per 1 million males and over 370,000 per 1 million females will develop cancer over their lifetime.”

In his comments to council, Robb Davis noted that the lifetime risk of respiratory cancer was about 10% or 100,000 in 1 million.

The numbers shown above are on the magnitude of 1025 per 1 million, a far lower added risk than the overall risk.

The EIR notes, “Long-term exposure to this concentration of diesel PM corresponds to an incremental cancer risk level of 235 in one million above the background level of cancer risk from TACs in the region for residential receptors.”  They add, “The estimated level of increased cancer risk based on SMAQMD’s Roadway Protocol (SMAQMD 2011) is approximately 197 in one million.”

They account for differences in those estimates to be due to “a number of factors including the meteorology that existed during the 10-day measurement, the potential for ‘linear enhancement’ because the wind direction is often aligned with the orientation of this segment of I-80, the fact that a nearby portion of I-80 is elevated which can result in the highest diesel PM concentrations being further from the freeway than for at-grade segments, and that vehicles often experience congestion along this segment of I-80 thereby generating more emissions than free-flowing traffic.”

The EIR continues, “YSAQMD [Yolo-Solano Air Quality Management District] does not specify a cancer risk threshold for sensitive receptors exposed to freeway-generated TACs. In the absence of a locally adopted threshold, a recommendation from BAAQMD [Bay Area Air Quality Management District] is considered. BAAQMD specifies a cumulative threshold of an excess cancer risk of 100 in a million for new sensitive receptors that would be sited in proximity to multiple TAC sources (BAAQMD 2010:2-5). Thus, both estimates of the incremental increase in cancer risk for residential receptors located on the project site are considered to be substantial.”

The EIR concludes, “While Mitigation Measures 4.3-5a, 4.3-5b, and 4.3-5c are expected to result in substantial reductions to exposure levels of UFPs and diesel PM, the level of effectiveness cannot be quantified. For this reason, and because ‘safe’ levels of UFP exposure and diesel PM exposure have not been identified by any applicable agency, or by a consensus of scientific literature, this analysis assumes that resultant levels UFP exposure and diesel PM on the project site could potentially be associated with a substantial increase in health risks. Therefore, this impact would be significant and unavoidable.”

The bottom line here is clear – the risks are substantial, but local agencies do not have standards whereby we can assess impact.  So they err on the side of caution and call them unavoidable and significant.

However, as Robb Davis argued a few months ago, in a real sense the risk of additional cancer and overall health impacts are quite low.  They claim that one problem with the analysis is that they do not address the issue of additional mortality associated with the risks over what time period.

Tim Ruff made a similar comment: “The EIR consultants came to the conclusion it is significant and unavoidable because there is no ‘proof’ so to speak. There are no levels set regarding safe levels and only studies that show how promising urban forests are and other mitigating factors. Given this uncertainty the consultants made that determination.”

However, this isn’t enough to satisfy Thomas Cahill.  He argues that this is an emerging area of science and he would use the term “dangerous” to describe what he believes is a significant added risk of death from exposure to the particulate matter at Nishi.

He shared some of his work in part of a major freeway project for the US EPA in Detroit.  The last two lines of that abstract are, “This result supports earlier publications showing the ability of very fine and ultra-fine particles to transport to sites well removed from the freeway sources. The concentrations of very fine and ultra-fine metals from brake wear and zinc in motor oil observed in Detroit have the potential of being a significant component in statistically established PM2.5 mortality rates.” 

He told the Vanguard, “There is a massive Environmental Justice aspect statewide, which we are working to prevent. That makes some of the comments on Nishi morally unsupportable.”

Dr. Cahill’s final comment to the Vanguard was the need to err on the side of caution or what he would call the “precautionary principle.”

He said, “After getting all the scientific information possible I would have to make my judgement with the ‘Precautionary Principle.’ This requires that in the face of uncertainty, I would have to choose on the basis of the most conservative estimate of the impact, which is almost always lower than  the scientist’s bottom number. In Davis, this means that (if) there is any reasonable chance that I and my colleagues are right, I would have to reject residential use and maximize protection of workers in commercial or research facilities. The best way to solve this is to have better data, covering at last a year and including all the most toxic components. This is what I recommended in  Jan 2015.”

—David M. Greenwald reporting

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. nameless

    This requires that in the face of uncertainty, I would have to choose on the basis of the most conservative estimate of the impact, which is almost always lower than  the scientist’s bottom number. In Davis, this means that (if) there is any reasonable chance that I and my colleagues are right, I would have to reject residential use and maximize protection of workers in commercial or research facilities. The best way to solve this is to have better data, covering at last a year and including all the most toxic components. This is what I recommended in  Jan 2015.

    What Dr. Cahill recommended is that his dept be given MONEY to study the issue further, which IMO makes his entire argument suspect.  If Dr. Cahill testifies FOR PAY in the lawsuit against Nishi, that also makes his testimony suspect IMO.  Note in his statements above, he states “IF there is any reasonable chance that I [am] right” – which indicates he really isn’t sure, it is just his theory at the moment.  The only real thing he is arguing for is BETTER DATA because he really can’t prove his contention.  So on this basis we should not build Nishi?  On a MAYBE?  Really?  Yet Dr. Cahill conveniently okayed New Harmony for low income folks right next to the freeway.  Sorry, but I find his claims less than convincing, especially in light of the developers willingness to mitigate the situation with filters and tree buffers as was done at New Harmony.

    1. The Pugilist

      I don’t think your comment is completely fair – I think he is saying that while he suspects the health impacts are greater than the EIR or current studies suggest, he doesn’t have the data to back up his point.  He wants to study them more and err on the side of caution.  Your view seems to be unless he can prove his contentions now, we should build the project. I get your point.  But I think that’s a little dangerous in and of itself.

      That said, the overall risk assessment seems low enough that we should build it, particularly with the mitigation and the relatively short living period at Nishi for most residents.

    2. Roberta Millstein

      Pugilist, Dr. Cahill said that he, personally, would take no salary.  But he needs a team.  Should he volunteer that others work for free as well?

      I think you are also missing the point of the precautionary principle.  You’ve got data that are suggestive of very harmful health effects.  Do you get more data or do you forge on ahead simply because you don’t have enough data right now?  The latter seems utterly foolhardy and in this case unethical.

      To me the fact that he is judging each site independently lends credence to his conclusions.  Not all sites are the same.

      1. Mark West

        The important question is not how great the risk of living at Nishi compares to zero risk but how it compares to living anywhere else in Davis. What is the magnitude of the increased risk?

        Dr. Cahill’s worst case projections are on the order of a few hundred health impacts per million people from a lifetime exposure to the air pollutants found at Nishi. We know however that by choosing to live in California our lifetime risk of developing cancer (just one form of ‘health impact’) is on the order of 100’s of thousands of cases per million people, two to three orders of magnitude greater. In other words, the increased lifetime risk associated with living at Nishi, (using Dr. Cahill’s worst case assumptions) are insignificant when compared to the lifetime risk of living elsewhere in Davis.

  2. Marina Kalugin

    I have a lot of respect for Dr. Cahill and he continues to work for free on many important topics.  I still don’t understand his point on New Harmony…….I didn’t have much time then either to keep up with the details and issues, however, I was shocked at that time to see his coming out in favor of that project and to see that it was approved and built given the continually increasing research espousing ills of being so close to vehicle pollution on the freeways.

    similar to Nishi that project really didn’t help with any long term solution to the housing situation….due to a huge jolt of new units that couldn’t be filled with those who are already here, live here, work here, go to school here, etc…developers sought out low-income people in places like Oak Park and Oakland to come to this lovely town and this lovely new development…

    that was hardly useful for those in town who were struggling but didn’t qualify or whatever




  3. The Pugilist

    This article basically demonstrates what I thought – the risks of health impacts and cancer from Nishi are far lower than the general risk of health risks and cancer.  Dr. Cahill wants a higher standard than currently exists, but needs to study the impacts to prove it.

  4. Alan Miller

    The fine particles travel far from the source, the winds prevail along the freeway, two years of study is needed, Cahill says “if” he is right.

    Will they also study Olive Drive to determine if it needs to be abandoned?  Are the long-term residents there in need of immediate evacuation?  What if Tom Cahill is right?  What if Tom Cahill is wrong?

    In my humble opinion, Tom Cahill and his allies are attempting to create, using his pedestal of “expert”, doubt in the minds of enough voters to prevent Nishi from passing, and his “science” is as viable as my statement at the beginning of this sentence that my opinion is “humble”.

    1. The Pugilist

      Again I don’t see the need to disparage Cahill.  He doesn’t have the evidence to back his suspicions, but he does’nt try to hide that from the public either.  I see him in a somewhat different light than some of the people who. Are backing his view without acknowledging the shortcoming of the state of the research.

      1. wig

        One of the issues here is the difference between an air toxics framework and a particulate matter or more general environmental epidemiology framework.  Air toxics frameworks are often used because the metric of concern is set at such a low threshold – 1 additional death per million.  And in California, black carbon has long been recognized as an air toxic and tends to dominate mobile air toxics analyses relative to individual toxic chemical components.   However, the sum of EPA listed air toxics in particulate matter or gaseous form does not come close to equaling the health effects found near highways and other large transportation emissions sources.  The best environmental epidemiology from advanced economies like the US, Canada and western Europe has found in whole city studies 50% or greater annual mortality risk for those most exposed – say those living within 50 to 100 meters of the source – for cardiovascular disease and for lung cancer (except among lifelong heavy smokers for whom the air pollution connection is obscured).  Similar relative risks exist for childhood asthma and for cognitive decline in adults.  Autism spectrum disorder risks seem much higher but the body of studies is still emerging.  For those children whose mothers’ full term pregnancies or their own first year of life residential locations have high relative exposure, the risks may be several 100% greater than for others who spend their pregnancies or first year of life in cleaner parts of the same cities.  These are all vastly higher relative risks than any air toxics analyses would show.  They are also based on the total impact of polluted air and not a finite number of individual components.

        Cheers, Wig

  5. nameless

    Roberta Millstein: “he doesn’t have the data to back up his point.

    This says it all!  You are conceding Dr. Cahill does not have the evidence to back up his contention! In other words, to date, it is only his theory!

    1. Roberta Millstein

      nameless, hello?  No coffee this morning?  That was the Pugilist who said that, not me.  Dr. Cahill has numerous peer-reviewed, published studies that back up his claim that there are serious health risks from living near a freeway (especially when elevated) and near train tracks, with prevailing winds toward the site (which there are, from the north and the south), plus air inversions in winter.  These studies are corroborated with the measurements that he took near the site.  Together, these make a strong case for Dr. Cahill’s claim that there should be no residences at the site.  Could he have more data?  Well, one can always have more data.  There is no conclusive “proof” in science.  But when your data suggests that there are serious health risks, do you get more data or do you just build and hope for the best?  As Dr. Cahill says, the precautionary principle dictates that you get more data and not build any residences for now; however, the City Council decided to go forward instead.  Now it’s up to us to protect Davis’s citizens.  If you want to play games by quoting someone else and attributing those quotes to me, that is a rather sad way to treat someone else’s potential future asthma, cancer, heart attacks.

      That “it’s only a theory” thing has gotten pretty tired.  It doesn’t work for evolution and it doesn’t work here.

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